Well, if it has to be matched to the CPU board then why not change the crystal in both?
Appreciate it makes them non compatible between different units but from what you're saying if there are two versions already then a third, if clearly marked, won't be too much of an issue?
The SiLabs MEMS oscillators were pretty good, low jitter and good stability, good enough that I think in another thread here one was used to fix a Tek 'scope...
If it *absolutely* has to be the right frequency and has to be a crystal there's always
http://www.krystaly.cz/en/ who can custom make to order and aren't expensive.
I think your emphasis in the quote about 'video clock generation' is misplaced, it's a TTL Inverter clock signal, it's not going to be great quality and while the jitter may be an issue with high bit rate telecoms or standards compliant video for broadcast, I reckon it'd be fine for a bowling scoreboard, you said it yourself, " just enough that the TV will sync to it"
They're cheap enough to try.