Well here is my personal experience OP. When it comes to "inexpensive sight pusher" options, a brass punch and small hammer probably is the best tool for the job.
I'm responsible for maintaining 130 pistols (Glock 17a &19s) for my department. I have been doing all the armorer work since 2012 and have removed /installed/adjusted for zero a lot of sights. When it comes time to remove/install rear sights, although we have a nice $150 sight pusher in the armorer's tool box, I grab a brass punch and a small ball peen hammer, because it's quicker and works just as well...And at a cost of less than $20 for the set for what is likely to be in your case a seldom used tool, it probably fits your "inexpensive" criteria better than anything.
All this talk of hammering and damage that voids a warranty.....well both rear and front dovetail sights sometimes, and in the case of specality/after market replacements almost all the time, require some filing/fitting for proper install. When done correctly no sight install requires hammering or hard pushing from a mechanical sight pusher. What a sight pusher does for most people is remove the need to file/fit the sights by providing some pretty good mechanical advantage....but that doesn't make the install better or ever right. I have seen both front and rear sights damaged (tritium viles compromised) when using a sight pusher and a hammer/punch without proper fitting first. It's a rare thing that requires some over the top gorilla strength, but I have seen the aftermath a time or two.
Any sight that is damaged from proper install, no matter the tool(s) used and warranty issues aside ain't worth having on a defensive pistol. And any company that won't stand behind their product when properly installed, not matter the tool used, ain't worth your business. Good luck on your purchase and install no matter the course you choose.