I have used a regular soldering iron to fix plastic trim for years, arguably with mixed results.
I had wanted a hot stapler or plastic welder for a while, but could not justify the price, most quality ones being well over £100, feeling I would only use it too sporadically.
Recently, I found this unbranded one online at a very competitive rate. I have been using it almost on a weekly basis since! Not only on my 4x4s, but also around the house, fixing the stuff around and in the workshop.
The kit includes 200 staples in 4 different shapes and thickness and a triangular blade. You can use the latter to cut through material, including plastic cords and straps, and to smooth plastic parts once you have stapled and soldered them, leaving a surprisingly even finish.
Verdict: Should have bought it sooner!
Price: from £35
Where do I get this? Online (eBay, Amazon, etc)