I'd try craigslist first. There are a ton of tractor places with used inventory around central Texas farm and ranch country. Sometimes Paige tractor has used implements. There's a couple of places in Taylor that have a lot of used implements.
I mow about 8 acres and do some light shredding. I recently bought a Big Bee 60" shredder for around $700. It is great for light use. My FIL has been a commercial mower for over 40 years and he swore to me that, for my use, it would be silly spending more money.
I have plenty of brush. Some is pretty heavy yaupon, persimmons and small elm/hackberry. I am looking for an older shredder with a fairly heavy frame that can take a bit of a beating for as long as it will last.
Then you need to find one that has upgraded gearboxes, spindles, heavy stump jumper, clutch, etc. If you only have a small utility tractor you may not have enough PTO hp.
Yep. I have an old 5 footer. The body has been rebuilt once already and in places the plate is rusting apart again around the frame and drive, but it just keeps on chopping. You can run it right through a bunch of yaupon or brush and is makes an awful bunch of noise but chews it right up. I'm going to re-weld some plate around it soon on the sides where it has rusted through but that gearbox could drive a tank.
If you have previously shredded persimmon then you know what to look out for later. If you haven't, your next trip will be like running over a million punji sticks.