Aren't they just a simple "V" belt? If so, all you need is the width of the belt; circumference which could be measured with some string round the pulleys and a tape measure and possibly the belt profile (also from the pulley).
It's a J-section 3-rib poly V belt - the same as the CCL Perform.
I THINK it's 635mm long, but it doesn't say on the belt and measuring the belt accurately is very difficult.
The Axi P/N is 400114 but you'll need to phone the order thro as it's not on the website or in the catalogue.
It cost £7.98 in May 2021.