Vintage Simmons Drums (UK) Users Group

Ok, so I finally got my hands on a working SDS EPB, and a bunch of
blank 27128 EPROMS. I've verified that they are all zeroed with an
EPROM reader. Here's the problem:

When I put some of them in, the input clip light stays lit while the
unit is in PROM play. This seems to happen with the AMD D27128-A and
some INTEL D27128-A, but not all. As a matter of fact, I have one AMD
D27128-A that did NOT clip, but when saving PROM, it got HOT HOT HOT!!

The INTEL D27128-4 seem to work great.

The MITSUBISHI M5L27128K work like a charm.

Looking at my SIMMONS branded chips, they mostly seem to be the
MITSUBISHI chips, except a couple are INTEL. 

Here's where I ask the question: Does anyone know of a good dealer /
seller in the US that might have the D27128-4 or the M5L27128K for a
reasonable price, that would sell to a private entity such as myself?
I don't mind paying a minimum of $100 or whatever, as long as it isnt
too high. I'm not made of money, yaknow. I've looked online at a few
places, and they don't seem to specify chip type other than 27128
(which is too vague). I know these chips are out of production.

Thomas