I've mackled-up my own budget spanner - at zero cost, thanks to a friendly local workshop who let me have a 4ft length of 1 inch square section tubing. (I think B&Q may also sell it if you can't get hold of it anywhere else).
It was then just a case of drilling a couple of 8mm holes in the original spanner, cutting a 6 inch length of tubing to give adequate clearance, drilling through both sections of tubing, and then bolting them all together.
(I bought a replacement spanner from the MGB Hive near Wisbech - for approx £5.50 - to keep in the car for emergencies).
It may not be pretty, but it certainly does the job - and it was dirt cheap!
