Dustcover mats are available from: http://synthronics.de/dust-covers-arp-1601-clone/
the slideswitches are close with the front panel, the mats for the switches must be able to move with the current position of the switches,
to fix this: remove the 11m metal spacer and use 12mm and a washer or use the 11mm spacer with 3-4washers.
furthermore out on all jacks around the TRIG/GATE switch and Gate-bus switch washers behind the panel - at this jacks we can't use washers between panel and the fixing screw - so you can use this washers for this solution.
a instruction how-to install the mats is described here: TTSH Dust Cover Installation