Best way caring for young Great Tit?

Hi

I had someone pass me a young great tit that was found along a road edge, it must be close to flight as the feather are quite a long way on, i did check back along where it was found but there was no obvious nest that could be seen and the area is rife with cats and cars of course,  tried the local vets etc but they are not interested in such a bird.   at the moment it seems quiet sitting still.  looking at photos online it could be about a month old

What would be the best to do ? i am loathe to just stick it out and hope its not killed by one of the local felines.  Could someone suggest a feeding routine that might be give it a chance to gain the strength to at least have a chance at flight.?

thanks

Mark