I have lots & lots of experience with PEX-A one-inch to 1-1/2" manual expansion. (Larger, I used electric at work).
Lever expanding 1-1/4" doesn't seem to take more strength than expanding 1/2 or 3/4".
Expansion rings at low ambient temperature can require a little more strength. (That's why Our Creator gave us hip pockets.)
Orange Depot sells rather inexpensive Apollo heads that fit the Uponor Wirsbo manual expander. A screen shot is below. Other places sell Uponor for most likely better quality and probably higher price than Apollo.
With some creative work-around you can expand manually with an injury. (See below for example)
Why The Work-Arounds:
About 5 months ago, I had 2 custom made metal plates, one 25 cm long, plus 27 screws installed in my dominant arm to hold shattered bones in place & replace washed away bone. I also had blood vessels and tendons repaired, plus head, leg and shoulder repairs. All of this right when I was in the middle of a PEX project using one inch & 1-1/4".
About 3 weeks after release from hospital I was back to using my Wiorsbo manual expander tool with 1" and 1/14" heads (with cast & immobilizer still on) by using a "Cheat-Of-Necessity" that you may be interested in:
Plan A: One lever in the good arm's hand and the other lever against a thigh, chest, abdomen, the wall, the floor,
ladder step, ceiling joist, or ...
Plan B: Cheater Bars on the handles (Haven't tried that. Don't know how clunky it will be to maneuver)
Plan C: One of my brothers uses knee-to-knee to expand, pushing his knees together like a butterfly's wings. Thinking he had an injury, I asked him why he was "kneespanding". "Because it's more fun."
Rings with stops will help you work one-handed, so I recommend those. (No need for Hand two to hold the ring against slipping)
I hope you project goes well & is a fun one!
Paul
PS: I don't know about others, but the older I get, the more Cheats-Of-Necessity get invented.