Here's another option (to pile onto the ones you've already found) & probably the cheapest you'll find a pre-made 6264 / 6116 or 5101 NVRAM adapter for:
http://www.denikar.com/ $16.00 (free shipping in the US)
If you're comfortable soldering you can also build your own adapter out of off-the-shelf parts for anywhere from $5-8 each depending if you take a risk on RAMTRON from Chinese sellers. Discussion about that toward the end of this thread:
If it uses RAMTRON & is compatible with your game(s), there's really not any difference in what the adapter does. The "magic" is the RAMTRON IC itself, the various adapters offered are just different implementations (ie. AnyPin is more versatile.. and that EmmyTech one won't require you to unsolder the existing RAM on WPC boards).
I make the Pinitech adapters and discounts are offered if purchasing more than 3x. I have no problem recommending *any* nvram adapters as regardless of which ones you purchase or if you build it yourself. They will get batteries off your board for the long-term and are probably one of the best upgrades you can do to your machine(s).
The "denikar.com" nvram adapters are a really great price. Personally if I was in the market for nvram (and not already building my own) I'd buy a bunch of those since the material cost for an adapter if purchasing RAMTRON from an authorized distributor is roughly $8-9 and the guy is only asking $16.00 with free shipping in the US & then offering discounts if buying multiple adapters. Not sure how he does it (assuming his adapters are factory assembled), but I know I can't compete with that price and had their been $16 adapters out when I started building my own I probably wouldn't have even bothered. I'm just glad someone's able to offer adapters cheaper to the community however it's being done.
http://www.pinitech.com - "Pinball Inspired Technology"
Kits, upgrades and test equipment for pinball machines