I can supply laser-cut stainless steel exhaust flanges for £23.00 each, plus postage and packing, as the only non-tubular part of the system. Please note that I only have them in long-stroke size, and they are suitable for any 498cc or 596cc long-stroke Scott engine. I got them made several years ago when having a batch of pipes made, and to get the price down I ended up with more flanges than the number of exhaust pipes ordered, so they are now surplus to requirements. If Alldens are having to get them made for their pipes supplying the flange with your order may well speed things along !
If you want one please send me a PM, email, or letter. UK p & p is £3.50, so a total of £26-50 each. My contact details are all listed in Yowl, under Eastern Section details.