Is anyone aware of any other mfg that has one of these products on the market other than the Ideal Twister?

Jes:
I did a quick google search.....nothing but "purple"

T&B has one under the marrette brand ,it is only listed for canada though

I don’t know of any other UL listed twist-on type either, but I prefer the Alumicon connectors anyway. They allow more wire combinations and take up less room in the boxes.

Alumicon

How would you all splice a #8 AL STR to a #12 CU STR in a box?

The other product I use from time to time if your box do have room I used Polairs connetor block they have one for small size but again just watch out the room in the box otherwise you will get it crowed pretty bad.

Jes., If you have 4X4 box it may be ok depending on the type of recetpale you are using and size of mudring you need to get it fit in.

Merci,Marc

#8 Al = #10 Cu in terms of ampacity; 60 degree table.

What size C/B protects this circuit?

Thanks for the replies.
There is no ampacity issue here, it's a 20A circuit. A number of mfgs make reducer/splicer devices that are set screw types.
Alumicon is not listed for larger than #10 AL.

They do make several sizes of traditional split-bolt connectors listed for copper to aluminum connection.
I don't have any specifics on them as far as minimum and maximum run conductor sizes go though.