We had a couple of early 1980's oscilloscopes at the museum which used the Mostek MKB36000 ROMs which are known to deteriorate over time (e.g. FROMs - Forgetful Read Only Memories).  One was a Tektronix 468 Digital Storage Oscilloscope which used a pair of the ROMs.  There was room to retrofit an adapter board to convert the 24 pin ROM socket to a 28 pin EPROM socket and we copied the binary contents of a pair of good ROMs to a pair of 2764 EPROMs.  We made our own adapter boards but there are inexpensive ones on the market such as these.  An adapter board is a bit wider and longer than the standard 24 pin outline but there is ample room in the 468.

We do not have these EPROMS available on eBay but can program and sell them on demand.  Contact the museum for details.