silly_cone:
On that note, I tried looking around for the hx711 op-amps, and they don't seem to be readily available.
There are dozens of eBay sellers of inexpensive HX711 breakout boards. You can also get them from Sparkfun, RobotShop, etc.
But if all you need is the "ability to detect a change" (your first post), then using analogRead with +SIG alone may be all you need to do (or +SIG and -SIG as per @Wawa). No one here knows what "a change" means, since you haven't defined it.