I used to have a Weird Science machine as a kid. It's awesome fun for two months, great fun for another two, really fun for another two, kinda fun for another two, "What the fuck is this still doing here?" after the last four. I guess it depends on how passionate you are about them.
Anyway, I got mine at an arcade and pinball auction. Mine was the only locked machine, so the stupids thought it was broken and thus no one but me placed any bids even though it was definitely among the better ones, condition-wise. Even scored me a decent few bucks back from the coin slots thanks to it being locked. I guess this tip doesn't help at all, though, since I figure said auctions to be much more of a rarity these days. Back then there was one like every weekend.