adapting sink drain from 1/14 to 1 1/2 at trap

I have a threaded sink drain that requires a 1 1/4" flanged tailpiece. the trap that is installed is a 1 1/2" slip joint (ready to accept a 1 1/2" pipe). It seems to me the easiest way to deal with this is to have an adapter at the p-trap, that will accept a 1 1/4" pipe I know there are 1 1/4" to 1 1/2" adapters, but all the ones I can find are a weld-type on the 1 1/2" side. Are there ones that are threaded on the ! 1/2" side, so I could just take the nut off the slip joint on the trap, and screw on the adapter? Or how else can I do this?

You use a 1 1/2" x 1 1/4" slip joint washer inside the slip nut.

ahh so simple thanks!