Here is how I thought I would do it before I decided I was stretched too thin as it is
Set up a dummy "web store" but it would obviously not take orders. The categories would NOT detail each and every code, just general categories. So for example the breakdown might be:
WW2 – Germany – Infantry – DAK
WW2 – Germany – Infantry – Engineers
WW2 – Germany – Infantry – Fallschimrjagers
and so on.
How specific you get might vary. For example, for Vikings it might just be:
Dark Ages – Vikings – Viking Infantry
Dark Ages – Vikings – Viking Ships
For ancients it would be:
Ancients – Romans – Mid Republican Roman
Ancients – Romans – Early Imperial Romans
Under DAK there might then be a listing of reach manufacturer that makes 15mm German DAK infantry. That way a gamer could then go look for those manufacturer's web sites (I'd put a link right in the listing). So you'd know your choices are Old Glory, Resistant Roosters, QRF and Peter Pig.
The problem with this is the web master(s) has to do most of the work.
I'd be happy to help set it up