If you are talking 989M2, HARD to find complete...
However, there are things you can do...
If you have the 989-M2 handguard, you're halfway home, just get a Walnut Marlin 70 stock,
sand the area until the handguard fits nicely, and sand the tip for the barrel band to fit.
If it's a 989 (with no M-2), any Old-style stock that fits a 70 (non-Papoose) will fit.
Also, if you wish to Upgrade to a Boyd's Thumbhole stock, or any New-Model (post 1994) stock,
use a DIP Marlin 795 trigger guard & trigger combo,
as the OEM Old-style trigger guard won't go on the new model stocks.
I'm actually surprised that one of the folks that has a stock duplicator hasn't made copies of the
989-M2 stock & handguard & sold 'em for new rifles...folks would buy 'em FAST!
One other final option...recently a guy took an M1 stock ($15 at a gun show) and fitted
a Marlin 795 in it. It takes a fair amount of carving skills, but it can be done with nothing more than
sharp chisels and a dremel for sanding