These are not exact replacement drivers but may work for your application depending on the voltage of LEDs being used.
Possible non-dimming replacements for Thomas Research LED driver LED35W-028-C1250 would be:
LED50W-042-C1190 - You will have to make sure your LED rated voltage is at least 21 volts
LED50W-040-C1250 - You will have to make sure your LED rated voltage is at least 20 volts
Analog dimming versions are the same replacement part numbers but have an extra -D suffix:
LED50W-042-C1190-D - You will have to make sure your LED rated voltage is at least 21 volts
LED50W-040-C1250-D - You will have to make sure your LED rated voltage is at least 20 volts
-Dimming and non-dimming options are interchangeable, it is only a matter of requiring the dimming function and/or stocking availability
LED50W-042-C1190(-D) has a lower slightly lower 1190mA constant current compared to original 1250mA, which may result in slightly less but barely noticeable brightness difference. This driver also has a minimum output voltage of 21 volts, compared to 14 volts of the original so you will have to make sure your LED voltage is at least 21 volts, and is within the 21-42 voltage output window of this driver.
LED50W-040-C1250(-D) has identical 1250mA current rating compared to the original, however the voltage output window is 20-40 volts compared to 14-28 volts of the original, so you will have to make sure your LED voltage is at least 20 volts and is within the 20-40 voltage output window of this driver.
Please see below driver specifications outline. However, please refer to original LED35W-028-C1250 Datasheet and suggested replacement driver datasheets LED50W-042-C1190 & LED50W-040-C1250 before ordering for exact specifications and to ensure they will work for your specific application.
LED35W-028-C1250 Original Driver Dimensions
LED50W-042-C1190(-D) & LED50W-040-C1250(-D) Replacement Driver Dimensions