Back in the day we chose to handload for just this reason - well, it was also less expensive compared to factory ammo.
I remember casting my own .358" slugs using a Lee, dual cavity mould. The bullet was a 160 grain gas-checked, SWC design and I generally cast them from wheel weights and other bullets I dug out of the shooting bank. My bullets were always a few grains heavy which told me they were softer than #20 alloy. Those were the days before the 9mm was even a consideration - the .357 magnum was king and I had a Dan Wesson (wish I'd kept it) that I picked up at Walmart for $145! I also had a Ruger Security Six, and a Ruger Blackhawk .357 magnum that cost a whopping $112! I loaded both .38 Special power and .357 magnum power loads based on the extremely generic Lee Loading insert, and later, Speer manual. I couldn't afford a sizer-lubricator at first and so my cast bullets lacked gas checks. I tumble-lubed my bullets using Lee's proprietary goo and I don't remember ever experiencing severe barrel leading - at least not any more than could be cleaned out by sending a few jacketed slugs down the barrel!
Today if I were to decide to load .357 hardcast I'd either source bullets of advertised hardness with gas-checks, or I'd set up to do it myself, but I haven't cast my own slugs in a long time. My basic goto alloy bullet supplier for the last decade has been Matt's Bullets, and these days they're offering a 165 grain hardcast with gas check that would probably be a very good choice for those who want to roll their own performance .357 loads. I source my .500 slugs from Matt's and have enjoyed great success with their 380 grain SWC-GC that I push to 1,450fps from my 4" M500. I've also used their 250 grain SOFT cast .430" HP slugs to make up a batch of .44 Special "hot loads" that clocked 800fps/355fpe from my CA Bulldog, and while it handled them well, I backed it down to 750fps/312fpe because - like, YOWZA that 800fps load was stout!
Anyway, I digress. Rim Rock Bullets makes a nice-looking 158 grain gas-check hollowpoint hardcast that is the bullet you want for 1,400fps/688fpe IF you plan to load your own and it's not hard...even in this overpriced, over-mechanized world, a simple Lee Hand press is really all you need to turn out a box of 50 while relaxing at the table. I would however suggest anyone loading pistol ammo add a Redding 10X powder measure coupled with a genuine balance beam scale such as the RCBS 505. The 10X throws charges for the 5.7x28 that are spot on using AA powders. I never run a progressive when loading performance ammo. Every step is by hand for the ultimate in reliability and quality.
I'd like to point out here that one of the major benefits of running hardcast lead slugs is they can can be pushed upwards of 100fps faster at the same chamber pressure as jacketed. Copper-alloy jacketed slugs have more bore friction and worst of all are the solid copper slugs because they can't compress to accommodate the barrel and are thus limited - you've probably already noticed that all copper projectile ammo seems inordinately slow compared to other types.