I know this is going to sound weird, but Fax your orders to him. I navigate the website, find his part numbers, type up an old school letter that includes all of my particulars, include a credit card number and Fax away.
I have never been limited on the number of items I purchase, nor had any issue whatsoever.
I realize that not everyone has access to a Fax machine these days, but there are plenty of free fax services like https://faxzero.com.