Hi Mike,
We're still using Linkpoint as far as I know. Although yes, the company seems to get bought and sold a lot.
The real problem is not in finding a gateway, it's in becoming a "credit card merchant". The gateway can typically only process for you if you are a merchant. (That's something the bank allows you to be.)
If you can't be a merchant then you can use a generic payment system like google or paypal etc. Integration is not trivial - as you're dealing with credit cards the process is quite convoluted - but several folks have done both already as far as I know.
Cheers
Bruce