For multiple reasons, geared D25 motors are used on all current 1/16 releases.
There is a lot of different manufacturers of geared motors with the compatible size.
Anyway, they are not easy to find sometimes.
You can find a lot of them, when searching for "geared motor D25".
Default values for both, Hetzer and Cromwell: 6V, 280RPM and 34:1 gear ratio.
You can use 12V versions as well.
25Dx52L HP Motor with 34:1 Gear 6V 285RPM - Pololu 1573 - Motor from Pololu.HP motor series.
You can find your local reseller here:https://www.pololu.com/distributors
JGA25-370 6V 280RPM - mostly available in China.There are some really good manufacturers, like Bringsmart and Aslong.
If you want to order from China, search for this manufacturers.
If you know some shop with compatible motors, please, add link to this thread.
Thank you.
POLOLU 1573 for Poland, Slovakia and Czech republic.
https://botland.store/dc-motors-with-gearbox/3608-25dx52l-hp-motor-with-34-1-gear-6v-285rpm-pololu-1573-5904422304522.html
POLOLU 1573 for EU.Next batch will be available in November.
https://www.tme.eu/sk/details/pololu-1573/dc-motory/pololu/34-1-metal-gearmotor-25dx52l-mm-hp-6v/
POLOLU 1573 for Germany.
https://www.exp-tech.de/motoren/dc-getriebemotoren/6924/34-1-metal-gearmotor-25dx52l-mm-hp-6v?c=1198
ASLONG JGA25-370 from Aliexpress
https://www.aliexpress.com/item/1005002667944001.html?spm=a2g0o.productlist.0.0.765e35e5qT3OBI&algo_pvid=79b390f8-13f6-4b8b-b3eb-6231d2a26003&algo_exp_id=79b390f8-13f6-4b8b-b3eb-6231d2a26003-7&pdp_ext_f=%7B%22sku_id%22%3A%2212000021626712176%22%7D
BRINGSMART JGA25-370 from Aliexpress
https://www.aliexpress.com/item/32363771997.html?spm=a2g0o.productlist.0.0.30593ccaOGlSD7&algo_pvid=72541661-3276-4382-9215-2ea83e3a04bb&algo_exp_id=72541661-3276-4382-9215-2ea83e3a04bb-5&pdp_ext_f=%7B%22sku_id%22%3A%2210000014544240204%22%7D