I haven't seen a replacement MAF wire assembly, but if they are out there and you don't touch the wire, they should work well.
I still think for $125 you are better off buying the complete MAF, that way if it fails, Rover will replace it under warranty wher if you get the insert and get it dirty, they will deny your claim.
Mike

 

About 9 mo. ago (5,000 mi.) I cleaned my "97 D1 maf & bought used one as spare.
No codes since.
It may or may not work for you, they are delicate, but to me, it was $6 well spent.
I also got 19 mpg (@65mph) round trip chicago to central minnesota & back

 

9 times out of 10, cleaning the MAF will kill it or only partially help on correcting the drivability issues. It will vary also between models, the Bosck Maf is very sensitive and will nearly always fail when cleaned, the older D1's were a little more forgiving.
Mike