We put a Raritan PHC in our C310 last year. Very happy with it. Less expensive than the PHII-not sure if there are any drawbacks compared to the PHII, but the basic pumping system seems the same.
The both use the same pump. The only difference was the base...the PHC was on "Compact" base.
Raritan has replaced the PHII and PHC with the PH SuperFlush. It still uses the PHII pump--which has been the top rated manual toilet pump in its class (used to be <$500...now <$1000 due to inflation) for 30 years. Keep it well lubricated and rebuild every 5-6 years (about $60 for the kit) and it'll easily last 20+ reliable trouble-free years
They've been able to reduce the price of the PH SuperFlush considerably (<$300 @ Defender, not sure if sbo.com has it yet) by redesigning the base to fit both the standard and compact version and also making it a "plug 'n' play" replacement for any Jabsco manual toilet. Yes, it does still cost about twice as much as a Jabsco...but you only have to buy it ONCE in 20 years.
I've never quite understood the logic behind the perceived need for a manual "backup" to an electric toilet. If you don't have even the 10-15 amps needed to flush a toilet, whether you can flush or not is the LEAST of your problems...Cuz you're likely not to have lights, steering, communications, maybe not even an engine...but you will still have a bucket and a line to put that over the side to "flush" it! So enjoy the "push button" convenience of your electric toilets...maintain 'em...don't flush wet wipes!!!...keep your batteries charged...and you shouldn't have any need to replace either one for years. But if/when you do, do NOT put a manual toilet in your "guest" head...why? Because it's guests who cause 99% of toilet problems...so the last thing you want to do is provide them with a toilet that requires 'em do more than push a button to flush it!