Shoprugernow has mag available for around $37 + sh.
I had a question concerning shooting .38 spls espcially since had a hjammed mag after accidentaly dropping a partially loaded mag. Here is their response:
"The 77/357 will usually function well when loaded with .38 Special. However, the left over space in the magazine allows .38 Special cartridges room to migrate, occasionally to where the rim of the top round gets caught behind the rim of the round below, causing a "rim lock" jam. The incidence rate of this malfunction is fairly low, and varies by ammunition type. The gun was designed to shoot, and will shoot best, with 357 Magnum ammunition.
We have no plans at this time to produce a .38 magazine"
Thank you for letting me know about the magazines. I just ordered a couple. I reload so I can down load .357 cases to 38 SPL levels if I want. I do that for my wife when she shoots her .357 revolver. That way we don't get that carbon ring in the chamber which makes it hard to eject .357 rounds after you shoot 38 SPL. Reloading .357 or 38SPL is easy, and the cases last a long time if you don't bell out the mouth much to get the bullet in. Also at 38 SPL levels I use plated bullets which are cheap. Also the .357 case reduces bullet jump which might help accuracy.
I looked at the scope rings for the 77/357 and found they don't have the 77/357 listed. The rings which came with the Ruger are the high, but I either need to raise my scope or cut a notch out of my bolt handle. When I work the bolt it hits the lever on the scope zoom, changing it from 12X to 10X. I could not tell for sure, but I think Ruger wants $40 + 40 + shipping. I think I will go after market.
I hope Ruger or someone starts making a larger capacity magazine. I sent my K77/357 in to fix the jamming problem. They said it might take a couple of weeks or more for them to get to it. I miss it already.