I thought that I remembered seeing a for-sale post somewhere on the internet for one of these a long time ago
I'm going to guess they're rare but I can't help thinking now of silly uses I'm sure you people could come up with for one of these on a 68040 macintosh 
I've got one, made by Adtron.
Requires System 7.5 minimum, and works with a 68040. It'll work with PCMCIA memory card, as well as more modern CF, etc. with proper adapters.
I never use it. Send me a PM if interested.
Tried to reply to your PM, but you need to change your account settings to allow private messages.
I have an Adaptec
SlimSCSI | 1460B
PC Card | Fast SCSI
Made in Singapore
P/N 1680800 A
It has a cable with a DB-25 on the end.