Hi. Your Tektro's use the most common pads as used by many different brand and/or models of brakes so there is plenty of choice.
Shimano pads are the B01S type which are exactly the same.
Random examples:-
www.wiggle.co.uk
www.tredz.co.uk
No need to get hung up on pad brand or type description as long as you carefully match the shape/outline to the ones you wish to replace then they'll work.
Choose from many well known or even unbranded pads from most sellers or preferred sources but suggest you stick with resin/organic compound options depending on what your rotors are suitable for. 😉
Shimano pads are the B01S type which are exactly the same.
Random examples:-
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Shimano Deore M515-M525-Tektro Disc Pads
Buy your LifeLine Shimano Deore M515-M525-Tektro Disc Pads - Disc Brake Pads from Wiggle. Our price $7.99. Free worldwide delivery available.

Aztec Organic Disc Pads, Shimano Deore M515 Mechanical / M525 Hydraulic | Tredz Bikes
Save 31% - Aztec Organic Disc Pads, Shimano Deore M515 Mechanical / M525 Hydraulic £8.99 or available with 0% APR finance on baskets over £99. All Brake pads are delivered free to the UK mainland*, 365 day returns & Price Match. Buy Now.

No need to get hung up on pad brand or type description as long as you carefully match the shape/outline to the ones you wish to replace then they'll work.
Choose from many well known or even unbranded pads from most sellers or preferred sources but suggest you stick with resin/organic compound options depending on what your rotors are suitable for. 😉