You would most likely be able to just swap one in from a vw/audi a type 99 relay, this will often go right in place of the std one, and give adjustable intermittant, with no extra wiring, the interval being set by the time diference between switching to intermittant, immdeiately of then on again when you want a sweep, it will then run at this setting until, changed/switched off/onto normal wipe.
tabetha