If your talking about the U-Joint on the
front drive shaft is tack welded in and is not classified as a replaceable part. Jeep wants you to replace the whole front drive shaft.
However if you take the drive shaft to a specialist shop they can tack weld a new one in and rebalance the shaft. That's what I did with mine on my 2007 built 2.8CRD JKU, plus they can replace the 'can' at the other end, worth doing while its there. Get then to fit a Spicer which they may have to order in, as I initially got a cheaper one fitted that was available and only lasted 2 years.
Its worth removing at the axle end every couple of years to check the flex / rotation as they can partially stick and it not obvious until it wares out the front pinion bearings in the axle. (Been there
)
If your taking about the axel shaft U-Joints just had mine done. Just had 56,000kms on them and each one was only articulating smoothly one way due to rusty pin bearings.
If it is for the front axel, Spicer Universal Joint kit 5-760X for DANA 30 in eg. a Sahara
https://jeepey.com/product/u-joint-a...26638sp5-760x/
If you've got a Rubicon with a 44 axel probably this one
https://jeepey.com/product/axle-u-jo...joint-5-7166x/