As I see it, there is no such thing as a "standard" chain. There are just many options for what will fit your saw. Chisel, semi-chisel, round chipper, skip-tooth, ripper chain, pro-aggressive, homeowner-almost-safe safety chain, etc. The only factors that involve fitting are the chain pitch, width of groove in bar, and number of drive links. Your saw ought to be .325" pitch and have 78 drive links. Same as many other brand saws use.
If your saw takes .325" chain with 78 links on a 20" bar - I know Lowes and Home Depot have Oregon chains that fit and work fine. May not be exactly whatever sub-type as original but fine just the same. Now - if you're saying your saw has some odd-ball bar that takes an odd number of drive-links - that's a different issue.
I kind of see it like tires on a new car. When they need replacement I suspect most people have no problem replacing with a different brand and tread design - but must use the same size.
I buy most of my chains in the pro-series from Baileys on-line. That being said, I've picked up chains many times at Lowes and Home Depot for my "el-cheapo" saws like my Husqvarna 455 Rancher and Poulan Pros. The plastic Husqvarnas are the cheap homeowner line and often come with weird super-safety chain types which I personally can't stand to use. Murder to sharpen once worn a bit unless the safety bars get ground down.