AV-8A/C / Harrier GR.1 in 1/48 is made by Monogram and Tamiya. The Monogram kit is far superior (yes it's true), but has been OOP for a few years. It's still pops up on eBay regularly.
The Harrier GR.3 in 1/48 is only done by Airfix. An older kit but there are upgrades by Pavla to improve it.
Sea Harrier FRS.1 in 1/48 is done by Airfix and Tamiya. The Airfix kit is better detailed, but I can't vouch for fit. The fit on the Tamiya kit is mediocre at best, and it needs lots of help all around.
Sea Harrier FRS.2 is only done by Airfix in 1/48.
As said above for the AV-8B Harrier II, Harrier Night Attack, and Harrier Plus, there are kits by Hasegawa and Monogram (except the Plus, that is only Hasegawa). The Hasegawa kits are better, but the Monogram kits are not bad (and come with more ordnance at least a full basic load out).
Hasegawa makes the only Harrier GR.5 and GR.7 kits in 1/48.
Those are what is out there.
F is for FIRE, That burns down the whole town!
U is for URANIUM... BOMBS!
N is for NO SURVIVORS...
- Plankton
LSM