You will not find a narrow (.265") smooth J frame trigger easily. They were replaced with grooved triggers in the very early 1950s:
• Late 1950 - Grooved triggers, already used on I frame target models since 1935, began a transition replacing smooth triggers as standard on all fixed sight I and J frames until completed ~mid-1951.
However, the good news is that the I frame trigger and hammers will interchange in your 30-1 with one exception; you'll also need to change the hammer spring (mainspring) strut from the 'forked' style your gun probably has, to the older ball/socket style with a ball on the upper end of the spring strut. (Unless you have a very early 1960 model 30-1, what's the serial #?)
• 1962 – Hammer to spring strut junction changed from ball/socket to the fork/pin, J frames only (c. #295,000 on the Chiefs Spl.)
Another option:
If you'd like a wider smooth trigger and for the reason Cal44's 31-1 trigger is wide and smooth:
1986 - New smooth forged combat trigger became standard: .312" J frame, .312 - .320" K, L & N, including MIM triggers, and in 2003 MIM .340" X frame trigger.
The .312" smooth trigger and hammer are easier to find and can still be found new. They are a drop-in for your gun. But of course, although seldom likely, the hammer and trigger may need slight fitting to each other if not bought as a used matching set.
And you won't have to bob an early, hard to find older hammer. Although you might be able to find an already bobbed hammer from the same period as your gun using the 'forked' style spring strut you need. Many bobbed hammers from I and J frames have been changed out now that those early I & J frames are so collectible. Check the classifieds on this forum and on Ebay for one.