Any suggestions for a passenger seat backrest 83 kz1100

Hi all, my partner is always complaining about feeling like they are sliding off the back when we go 2 up. I wanted to surprise them with a backrest so they can feel a bit more secure on the back. after searching around I wasn't able to find much online. Any suggestions for places to look or other models' backrests that will fit my bike, or yall think I might be SOL? I was thinking of trying to fab something up out of Lowes hardware but accounting for my lack of skill I would rather avoid that option. 

Some K&G luggage racks from back in the day came with a sissy bar or backrest, including at least one adjustable version.  The racks are universal fit and can be listed in all sorts of ways on EB as K&G or KG and often times according to whatever motorcycle they were on.
Here's a pic of my 1981 KZ650-CSR w a bolted-on sissy bar (non-adjustable ).

I found this AMCO backrest/rack used on Ebay.  It was removed from a KZ1100A and may fit other models.My wife refuses to ride along without the backrest, so it gets used quite often.It is adjustable front to rear, and removable when not needed.  The rack shelf provides durable support for my Tourmaster Cruiser luggage bags.

Aschco (Sp?) and Larco are a couple of other vintage brands. Some of the Aschco racks are almost identical to the K&G that I have. And I think one or more of them made universal fit sissy bars.