Dick Tracy may have been Stembridge or Ellis Mercantile.
Both out of business now.
But, equivalent Full Flash .45 acp movie blanks are available from ISS props, or Joe Swanson blanks - (both have websites.)
I have several ammo cans full, they are great in a 1911, but, too much blank for my subs.
The DT Thomspon's will have been adapted like most other weapons with a BFA restrictor threaded into the end of the barrel, the flash just finds the holes in the various muzzle devices. Same as it does with the bird-cage flash eliminator on an M16, or the three hole brake on a PPSh41, I don't know what physics are behind it but it goes in the direction it's guided by the militarybmuzzle device after leaving the regular movie "hex" shaped restrictor they all have in the barrel.
The Ak47 with the iconic slant brake are annoying as the flash goes upwards at 45 degrees, and never looks quite right.
I just put a Howell Arms "Blank Only" barrel (they have a website) on my M1 and it is awesome, comes with two separate restrictors.
I use Atlantic Wall Blanks now, as personally I do not like the damage the bigger loads/mixes inflict on the old guns.
And Atlantic Wall are more reasonably priced, IMO.
Good luck with your 1928!