Everything is possible in theory... I have actually stumbled upon a number of eBay "portals" while searching for something. They mostly simply echo the listings and I'm not sure what the point is, probably leeching advertising income.
But, the big but - I believe the amount of work needed would be immense. eBay pages are very complex and they can (and will) of course change them at any time without warning, so the parser would need to be complex as well and might require changes quite often.
Add to this the endless ways of mispelling and misnaming the products, differences between national eBay pages, etc, and I'm afraid implementing anything like this would be feasible only to eBay themselves, having direct access to the databases.
Good idea though - I try to achieve the same relying on my excellent memory