390X memory HELP!

[aarontring]

OK, I'm getting to the point of esploding, here. I had a SODIMM go bad in my 390X (450MHz P3), and have, so far, bought 3 memory sticks for it, granted from recyclers or from "obsolete" inventory at repair shops, but none has worked, though one turned MemTest86 redder than Rudolph's nose. Fortunately, I've spent less than $15, but my wife is getting frustrated with me for many reasons related to this.
Sob story aside, I now have to resort to eBay, and I need some seasoned advice. I've seen posts relating to machines like mine using "low density" memory, but mine doesn't appear to be such. At least, it doesn't look like any of the ones on eBay. Is that because it's only 64MB? Really, the low density stuff on eBay seems to cost more for the kind I have, usually about double for same speed, same capacity. If I'm gonna do it, I'm gonna do it like I mean it, so we're talking a 256MB or, maybe, a 512MB. I'm reluctant to buy a 512MB, though, if I'm going to exceed some limit and have yet another cool-looking but useless chunk of green plastic. Any information on this would be extremely helpful.

Thanks.

User edit: I broke down and went to a reputable repair shop who happened to have a batch of SODIMMs. All they had in my speed were 64MB, but I just wanted to get it up today! Got the "new" card home, and it froze at the OS select (I have 98 & 2K). I ran MemTest and it turned red immediately. After beating my head on the table a few times, I took the new card out and booted back up, forgetting that the MemTest disk was still in. Turns out it was MY card that was bad, and, while it still won't run the wireless, it now runs as fast as it did with the two DIMMs I originally had. Go figure.

[RealBlackStuff]

Check my post of 05/03 for cheap compatible RAM, fresh from a PA factory.