The links provided below are to web sites that have historical information about Herbs & Spices as well as some purveyors of spices, including some "hard to find" spices like Cubebs, Grains of Paradise and Long Pepper which were more common in the cuisine of the Middle Ages & Renaissance
Online resource for historical herbals
List of references to food preparation from John Gerard's Herball or General Historie of Plantes
Detailed information on spices and detailed discussion their history, chemical constituents, and the etymology of their names
Blog on Medieval Gardening
Supplemental website by the author of "The Taste of Conquest" to fill in the gaps with graphs, charts, recipes & links to other websites about spice history.
Disclaimer: I do not specifically endorse any of the following, but they may have supplies you are interested in.
Wholesaler of Herbs & Spices
A variety of ingriedients available including Herbs & Spices.
Has several Old World perennials including Skirret.
Gourmet Spices, Herbs, Tea, Essential Oils and Potpourri at Wholesale Prices.
Chemical and Pesticide Free Herbs & Spices dried in small batches at low temperatures