The correct variable-speed drive belt for the Raglan "5-inch Lathe" These belts are high-quality, industrial-grade belts made in Europe. installation tip: The manual suggests swivelling the layshaft housing about bolt 'D'. However, a better solution is to remove the grub screw (at the rear) securing the shaft to the housing; the housing can then be slid off the layshaft allowing it to move further, thus giving enough clearance to remove & refit the belt. The earlier "Little John" lathe belt is different and can be found here
For the twin V-belt drive you'll need 1.6 metres of T-link belting in an "A" section. This can be made into two belts of an identical length (and so ensure that the spindle runs smoothly) and can be fitted without having to dismantle the headstock. This type of  belt can be ordered here -make sure that you select the "A" section: https://store.lathes.co.uk/belts/nu-t-link-v-belt