Just get an email that I found a company that can make the pulleys looks like the GT2-20, but in size T2.5 - 19 Tooth - 8mm drill - 2x M4 grubscrew holes. Now the question is what they are going to cost (I’m waiting for reply).
When this becomes too expensive, I’m going to look for the GT2-20 because the original pulleys are really bad, I do not understand that Velleman have chosen for this pulleys…
Edite: Unfortunately, that is getting too expensive, this is the manufacturer’s response:
20 pcs. AL16T2.5/19-2 3 PART PRESS TOGETHER with 8mm BORE + 2 x M4 G/S @ £14.58 GBP each. Delivery : 7 working weeks
Terms : Payment with order. Shipping : not included. VAT is chargeable if you do not have a valid EU VAT number.