Can you be a mite more specific, and if possible post up some pictures please? It seems like these are powered hand tools, such as planers and circular saws. I have a planer like that (the chip output is actually a parallelogram - it's not even square!). There are some options you might consider:
0. Check there isn't an adaptor available for the tool in question as a spare part. Power Tool Spares (S'oton) and Miles Tools (Yeovil) are places I'd start with, as they have good web sites with exploded diagrams and lists of parts.
1. If you haven't got one, get a hot-air paint stripper. They're not expensive, and useful for all sorts of things, including even bending thin wood effectively. In particular, they're good for re-shaping uPVC pipe and shrinking heatshrink.
2. uPVC pipe can be re-shaped with hot air (and a bit of practice), but if the outlet is itself plastic, consider making a male former in wood (or MDF), so you don't melt the wrong thing by accident. You can soften it with boiling water, but you can't keep it hot enough (usually, in my experience) to get a decent new shape to it. I'd pre-warm it in a simmering pan of water, and keep it at temperature with a hot air blower. If you have no fear you can also (theoretically) do it with a propane blowlamp, but I've never succeeded in not burning the outside of the pipe that way.
I'd start with a longish piece of pipe get the shape right, at the end, then cut it off to length afterwards. Cutting to length first does let you immerse the piece, but the whole lot goes plastic and you can't easily grip it to work on.
If you can't get the shape easily from one piece, consider doing parts of it by heating and then weld the bits together with solvent-weld "glue" from a builder's merchant. It really is welding (not glueing), and the joints are very strong if left for 24 hours before use. You can join most pipe material edge-to-edge without much loss of strength, and you can always reinforce the joint with strips of plastic glued over it later.
I've had great success 'unrolling' uPVC pipe by slitting it with a hacksaw (or on the bandsaw) then heating it and pressing it flat. The resulting plastic 'plate' makes good repair patches, washers, etc. If you have some unused large-ish wall tiles (and you can get permission from the Domestic Controller), heat two of them to about 90 deg C in the oven (bring them up to temp slowly so they don't crack!) Then put your flattish piece between two so it cools slowly as they do.
3. You used to be able to get giant-size heatshrink for drain and drainpipe repairs, and for going between imperial and metric sizes. It's not like the stuff for electrics, in that it's not at all flexible once shrunk. It shrinks down well and is quite thick. BUT... I haven't seen it around for a while, and it was very expensive for what it was (in 4" size).
Hope something above triggers a bright idea...
E.
