Common acid fixer makes a fine stop bath, but developer carry over shortens the life of your fixer. I guarantee your lab is using an acid stop if they use Xtol.
FWIW, I'm still using a bottle of stop bath I made up from Kodak Indicator Stop Bath concentrate in 2006 or so. It sat in storage all this time, in weather from -10C or lower to above 40C in the storage shed the last five years -- and it's still yellow (the indicator shows it still has the acidity to work as it should). You can use white vinegar, diluted 1+2 with water, but indicator stop bath is actually cheaper, because the indicator lets you reuse it for a long time, and know when it's done. I bought the chemicals to make my own, too -- 75% acetic acid (much cheaper than glacial, and safer to work with) and bromocresol purple (the indicator that goes into it), then found my old bottle of concentrate, so I have a lifetime supply of stop bath (well, probably not, in my experience printing uses it up a lot faster, because more developer carries over and you're developing a lot more area anyway). For film, indicator stop bath is virtually free -- a $6.99 a pint, which makes 8 gallons of working solution, it'll stop hundreds of rolls. Shipping is annoying, though -- it's ORM-D, which means you'll have to order it from a Canadian source and it ships ground only.
Keep checking the top bar of your Photrio pages, I keep seeing ads for a Canadian chemical supplier up there.
I've used Parodinal quite a bit (Rodinal work-alike made from paracetamol aka acetaminophen). What I'd suggest is to use it (instead of diluted Xtol) where you want maximum apparent sharpness, don't mind losing half a stop of film speed, or you're willing to add 40% to recommended dev times and reduce agitation to every 3rd minute to get back that lost speed and another 1/3 stop. It shows its true nature best at the 1:50 dilution. The other place Rodinal shines is at 1:100 with just a single inversion every 15-30 minutes, and standing for an hour to two hours. You'll have grain, but you'll see strong compensation even with the 3-minute agitation cycle, and more so with stand, plus you'll get edge effects that increase apparent sharpness by bumping the local contrast at already high contrast edges.