There’s a rumor that the Raritan PhII pump will bolt right on.
Sorry, not true. The PH SuperFlush (current version of the PHII toilet) base assembly mounting bolt pattern is an exact match for Jabsco and other manual toilets, but the PHII pump is not a "plug & play" replacement on any other manual toilet base. Raritan used to offer a PHII "conversion" (lower base and pump assembly without the bowl, seat and lid), but they've apparently discontinued it 'cuz it's no longer available from any retailer. A couple of 'em are still showing it, but they're always "out of stock."
However, as we say in the South, "there's always more than one way to skin a cat." And with some creative digging I just may have found a way that'll work for you: You can buy JUST the pump from a bunch of retailers. Amazon has the best price I could find for it: $220
Amazon.com: Raritan PHII Pump Assembly (Only Complete): Sports & Outdoors
And you can buy JUST the base assembly from this retailer
Raritan 1248W Base Assembly for PHII and PHEII Toilets – RAR1248W for another $53...which would bring the total price to only $53 more than you'd pay for a pump if it were plug & play on your headmate base.
It's not the PH SuperFlush base, so there's no guarantee that the mounting bolt pattern will be a match for your HM, but it's no big deal to drill a couple of new holes and fill a couple. And you'll need to buy a pump handle, but those are standard broom handle diameter so you should be able to find a nice piece of aluminum pipe (heavy enough not to kink when you use it) or just a broom handle (paint it white or any color you like) and a bicycle grip to become the handle at any big box or hardware store.
--Peggie