I recently picked up a Bogen/Manfrotto #144 tripod (also known as #3001) with a #3025 compact pan/tilt head at a local 2nd hand store for all of $10. I just put a $15, Chinese-made (but surprisingly NICE) Arca-compatible quick release platform on it so it will be usable with my various camera gear. It'll make a good CHEAP backup to my Gitzo and Bogen/Manfrotto tripods. The #144 tripod uses thumbscrews (plastic caps, but with two shorter "ears" instead of the one long "lever" on the style that broke).
The reason this tripod was in the 2nd hand store was probably the "wobble" in the head.... Which was nothing more than loosened set screws under the mounting platform. I tightened those and put a little Loctite on them... dusted off the rest of the rig... good as new!
Old Bogen/Manfrotto tripods rarely die. But if you look closely at that replacement part (
https://www.bhphotovideo.com/c/product/564195-REG/Manfrotto_R055_109_Replacement_Leg_Lock_Lever.html) it's fairly obvious why it would fail. There's a "crimped" section on the threaded bolt right near the head, which no doubt weakens it considerably. That, along with the leverage that can be applied on the long plastic "handle" is a recipe for a failure! Maybe it's deliberate. I wouldn't be surprised if they crimp those like that so that the bolt will break before you over tighten it and potentially damage other parts of the leg lock mechanism. $16 apiece for replacements is absurd, though!
I'd wager that a different replacement part could easily and inexpensively restore the OP's tripod to full, safe, and secure working condition. I don't know what thread Bogen used, but it's probably something pretty standard. I'd go to a local hardware store and look for thumbscrews with oversize heads similar to this:
https://www.bhphotovideo.com/c/product/778777-REG/manfrotto_rh02e001br_replacement_lock_off_knobs.html?sts=pi&pim=Y Plastic capped ones would be fine. They come with two "ears" and in other knob designs... choose whatever seems most comfortable. The bolt itself just needs to be the right diameter, thread and length to do the job. "Generic" thumbscrews at hardware stores will only cost one or two $ typically... much cheaper than that "weakened" Bogen/Manfrotto part.
Using a stronger, replacement thumbscrew on there, you'd have to be careful not to over tighten and damage other parts of the mechanism. But, just using some common sense in that respect, the tripod should do it's job well.
Other Bogen/Manfrotto parts that are unique, where generic items can't be substituted, can often be found at:
https://bogentripodparts.com/index.html Or just watch your local 2nd hand store for a deal on a decent tripod! (There are a lot of utter junk tripods there all the time, too. I pass on those!)