You can get a pair of compatible cache chips from Digikey for about $30 shipped.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=CY7C1347G-250AXC-ND
Of course, soldering it into place is challenging, but not at all impossible.
Alternatively, Sonnet has the 400MHz/1MB upgrade for $29.95 + shipping.
https://secure1.sonnettech.com/product_info.php?cPath=22_91&products_id=251&osCsid=27d343a2b18c646224a363e778001f87
Because it's going in a 6100, the fact that Sonnet may not work with a Fast & Wide SCSI card isn't really a problem. I think Sonnet actually fixed that, but in the early years, the NewerTech NuBus upgrades worked with the FWB JackHammer card and the Sonnet upgrades did not. And, IIRC, neither worked with the Initio SEIV card.
If you look at the same card under "Special Deals" on Sonnet's website, it's $39.95 instead of $29.95, so use the "Processor Upgrade Cards" category in the side bar to get there. They don't seem terribly consistent in their website pricing.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=CY7C1347G-250AXC-ND
Of course, soldering it into place is challenging, but not at all impossible.
Alternatively, Sonnet has the 400MHz/1MB upgrade for $29.95 + shipping.
https://secure1.sonnettech.com/product_info.php?cPath=22_91&products_id=251&osCsid=27d343a2b18c646224a363e778001f87
Because it's going in a 6100, the fact that Sonnet may not work with a Fast & Wide SCSI card isn't really a problem. I think Sonnet actually fixed that, but in the early years, the NewerTech NuBus upgrades worked with the FWB JackHammer card and the Sonnet upgrades did not. And, IIRC, neither worked with the Initio SEIV card.
If you look at the same card under "Special Deals" on Sonnet's website, it's $39.95 instead of $29.95, so use the "Processor Upgrade Cards" category in the side bar to get there. They don't seem terribly consistent in their website pricing.