If you're interested in jacketed bullets, be sure to buy any Sierras that you want, when you see them. Sierra doesn't like running the uncommon handgun bullets, and they can be unavailable for long periods of time. Since the little .32 is their least popular handgun bullet... it has the lowest priority.
Hornady is better about running their XTPs, but the 85s and 100s still disappear fairly quickly during any 'shortage'.
Speer Gold Dots are decent, but I rarely see them. I'd be surprised if anyone still has any in stock right now.
Brass is harder to get. Starline shows that they'll be
running some in February, if you wish to get on the backorder list.
Otherwise, you just have to hunt and peck your way through retailers and websites, until you find some. (Or buy factory ammo.)
For alternate cartridges...
The SP101 will not set off .32 ACP and .32 S&W as reliably as the other Ruger .327s. I would avoid them, altogether. But, .32 S&W Long and .32 H&R will be just fine, should you wish to shoot them.