Buck and Buck does provide a comprehensive guide of adaptive clothing (http://www.buckandbuck.com/adaptive-clothing-guide.html), albeit it is mostly about their products, it also has a lot of good general information based on different health conditions.

Disabled-World has information about adaptive clothing and links to manufacturers and size conversion charts (https://www.disabled-world.com/assistivedevices/adaptive-clothing.php).

Silvert’s Adaptive Clothing – on Amazon: https://www.amazon.com/s?k=adaptive+clothing+for+seniors&crid=226EEB2678RPP&sprefix=adaptive+clothing%2Caps%2C168&ref=nb_sb_ss_ts-doa-p_3_17 to link for affiliate’s program.