Trellis spacers

Hello everyone
Does anyone have any tips on the best spacers to use behind trellis to keep them away from the wall to allow air passage? I've purchased Gardman trellis spacers in the past but they're difficult to find now and P&P on websites is way to high for a packet that only costs a couple of pounds in the first place. What do professional gardeners use I wonder - I can't image they spend money or time searching for little plastic spacers and wondered whether there is a long tubing available that can be cut to requirement?
Any ideas?
thanks!