For used parts, you can use an online junk yard search engine:
www.car-parts.com
In Arizona, for new oem parts;
Largest Car Part Warehouse | Replacement Auto Parts Online | AutohausAZ is a great source for parts and then, back east, if you have time
www.fcpeuro.com is great with a lifetime warranty, on everything they sell.
For the convertible top; I would start searching online, there are some brands that offer a lifetime warranty, being in the Southwest the sun is destructive to convertible top, a lifetime warranty makes sense and then, call around to local upholstery shops that do convertible top installations, to find one that can do the work for you, possibly, they might have a top supplier recommendation.