The Progressive brand rear shocks (I have on my R65LS) work pretty well, especially if you are >200 pounds or carry alot of stuff. They aren't really damping adjustable so you might have a mismatch situation with your setup. On the plus side, they are inexpensive, and well made, but no frills and if you cannot get close enought to want you want with the spring preload adjustments, well, you bought the wrong shocks.
The Hagons are definitely a significant step up and several folks have them and are pleased. They'll setup the shock to your weight/load expectations and they standby their product. More $$$, but more adjustment potential, custom setup, and very good quality, IMO.
Another option, but which has been somewhat on again/off again for availability is IKON - these were formerly known as KONI brand and are comparable in some ways to the Hagons. But, KONI went out of business many moons ago, and was resurrected as IKON some years back. i think they make good product but availability - at least in my area, has been sketchy lately.
I'm am putting a Sputnik sidecar on my 78 R100/7 - the R100 has some old school WorksPerformance AIR shocks on the back of it (PO had them put on from another older DS bike) Amazingly, these still seem to work good on solo bike rides, and they hold air well. I am going to try them with some more PSI when I get closer to getting the chair bolted up to the bike. I don't think that they make these in the shorter length (13") for the R65 frame though. They do offer several models for vintage bikes, so maybe they do - I haven't checked ... but they're still in business!