looking for some,any ideas?

If I couldn't find any I would buy a Lee push thru bullet sizeing die as close as I could get on the small size. polish it out to 427.

Then push 429-430 pistol bullets through it and get what you want. I push 429 bullets through a 416 die and shoot them through my 416 taylor.

Works well should be very easy to do 430 to 427

Even more "extreme" we used to size down 230 grain FMJ .45 ACP bullets to .429" for metal falling plate competitions in .44 Magnum.

This was thirty years ago when FMJ .44 Magnum bullets were not made.

Usually in an RCBS Lubrisizer with the pressure turned off as all that was wanted was sizing not lubing. We just used standard .429" dies too!

So using an good STEEL lubrisizing die of .427" in an RCBS Lubrisizer would easily size your regular .429" (44 Magnum) JSP bullets down to .427"!

Trying to size jacketed bullets in a regular Lyman or RCBS lub-sizer is a bad idea. Might as well go out and buy a new one before you start to do it. On the Lee pushthrough dies there is a 0.001" spring back on jackeded bullets so if you want .427" you will need to get a .426 die.

I have read several times that due to "spring back" the jackets will be loose on bullets
sized down. It was claimed that they had to be bumped up. I have no personal experience with this.
Good luck1

When I size the 429 bullets down to 416 the core moves out of the jacket about 1/32 at the nose. I have shot deer with them at Muzzle vel of 2650 worked well.

When I maded my 416 die I would polish run a bullet thru polish run a bullet thru until they came out.416

I think Remington was the only maker of the 44-40JSP. You can easily size down 44mag bulelts to work in a Lee 0.427 die. I do it for cheap plinkers in my 404j. I size to 0.427" first then again in a 0.423" die using Imperial sizng wax. You do need a solid press & bench setup though.
If you are shooting these in a revlver, do yourelf a favor & go lead. The gun will like it better & yo ucan make the bullets any size you like.

The LEE size die should work fine but you might check your groove diameter in your gun first. If it is bigger than .427 you can use 44 mag bullets. Remington did sell bulk 44-40 bullets and I think Midway used to have them.