These motors have been built into working locomotives
These motors are from Changzhou Jkongmotor Co. At time of writing this link to the manufacturers web page worked. Frame sizes of motors I have used are 42mm and 86mm.
Another motor suitable for 5" has been tested 'on the bench', the 24V 220W Nanotec DB59C024035-A. Link to Nanotec data.
The JK42BLS04 (or apparently identical type) is available in UK from RS components - RS web page
The Nanotec DB59C024035-A can be ordered from Nanotec, Munich (see Nanotec link above **tip** beat brexit and save!!), also available in UK from Farnell - Farnell web page
All these motors may be driven using the STM3 ESC dual brushless motor controller (see under 'Electronics' tab).
Other motors were ordered directly from China (use Jkong motor links above f.f.i.). When seeking quotes, be aware of delivery charges and that duty will be payable on top.
These motors are all rated for industrial, continuous use. The links above lead to the full motor specifications detailing, at very least, continuous current, voltage and output torque and power ratings.
Note also motor power ratings are mechanical output powers. Maximum electrical input powers will be greater.
If you have the time and patience you can probably find many more suitable motors at sites such as alibaba.com
Here is a spreadsheet showing calculations used in designing above motors into real miniature locomotives!
Please do not waste your time looking at motors intended for toys, drones, RC models etc. Brightly coloured motors the size of a C cell battery are **NOT** going to deliver 1kW of power - not after the first few milli seconds anyway. Stick to industrial ratings for traction / locomotive use.