Wild/Perennial/Babington leeks

Hi and welcome to Garden & Gossip!  Most of us are in the UK or Europe. I don't know of any stockists in the US. Sorry.
Neither do I know what the US rules are about the import of plant material.
One UK supplier says that they cannot send worldwide due to plant health regulations . https://incrediblevegetables.co.uk/shipping-returns/

Thank you and thank you for your reply. 

I'm pretty sure shipping to the US is permitted, but it may be burdensome.  I've been trying to work through Chiltern Seeds Ltd <info@chilternseeds.co.uk>. They may have stock later this year.  I am trying to secure some (about 20) Babington bulbils and some (a packet of 50-100) seeds for Ramsons.  

I went on the USDA website and completed an eFile application.  I received and exemption letter; however, Chiltern replied that they could not work with that.  I've attached the letter I received from the USDA saying a permit (on this end) was not needed, however, the mailing could be subject to inspection and needs a certificate from over there documenting that the seeds will not pose a risk to US ag. 

That is, there is a requirement that a phytosanitary certificate be included with the shipment.  The phytosanitary certificate must have been issued not more than 15 days prior to shipment from the country in which they were grown and must be one of the following:

• Signed original (hardcopy on plain paper or security paper that is wet signed or digitally signed); OR
  
• Scan of signed, original hardcopy uploaded to Customs and Border Protection’s (CBP’s) Automated Commercial Environment (ACE) using the Document Imaging System (DIS); OR
  
• Electronic phytosanitary certificate created and shared through a participating country’s ePhyto system (digital exchange).
  

The phytosanitary certificate must contain the following information, unless stated otherwise :

• Certify the place of origin for all contents of the shipment;
  
• Certify the shipment has been inspected and/or tested according to appropriate official procedures and is considered free from quarantine pests of the United States;
  
• Certify that the shipment conforms with the phytosanitary requirements of the United States and is considered eligible for importation pursuant to the laws and regulations of the United States;
  
• Identify the genus;
  
• If individual species or cultivars within a genus have additional restrictions, then identify the species or cultivar;
  
• If there are no additional restrictions, then the species or cultivar is strongly preferred;
  
• If the plant is budded, grafted, or otherwise contains interpolated plant parts, then identify all plant parts (e.g., interstem, rootstock, or scion) that belong to restricted taxa to the lowest regulated taxon (genus, species, cultivar);
  
• If a hybrid plant has NAPPRA parent(s) (one or both), then regulate as NAPPRA;
  
• Hybrids may be listed as hybrid, hybrida, hybridum, hybridus, or hybr.;
  
• If a hybrid plant, then list the parent taxa if they are known;
  
• Intergeneric and interspecific hybrids must be designated by placing the multiplication sign "x" between the names of the parent taxa; and
  
• If the hybrid is named, the multiplication sign "x" may instead be placed before the name of an intergenetic hybrid or before the epithet in the name of an interspecific hybrid.
  

NOTICE: PPQ recommends that the information on the phytosanitary certificate, container, invoice, and packing list match and be written in English (or fully translated to English) to avoid delays in processing.

I am not at all familiar with the permitting process in the UK & Northern Ireland and in Ireland.  Is securing a phytosanitary certificate over there a significant burden?