Olson parts are often available on eBay, whilst they are wired internally with 2.5mm wire often the input lead is only 1.5mm. I have a couple of these blocks and replaced with output lead with 2.5mm cable as well (only as I often plug in multiple power amplifiers into each block). I also usually wire out the neon, don't know if makes much difference, just seems like good practice!

Mr Perceptive