Replacement motor are replacement motors available for model #U2-20 box fan? If so what is the cost?

Sure - but is the price of the replacement cost effective?

fans that oscillate but don'e spin suggest a separate small motor for that action
the fan not spinning suggest a failed motor
mostly it is not worth repairing fans as the parts are not readily available and the labour and parts will out weigh the cost of a new one
take it to an appliance centre for a correct diagnosis then make a decision.

You need to post the make and model. Also realize that the motor could be custom made for that company or by that company and a replacement might not be available or it might cost as much as a new fan.

hi Ryan.
How to Fix a Box Fan. Box fans work by having a set of fan blades attached on the shaft of a small motor. The motors and bearings on box fans have a tendency to go bad. Here is how to fix a box fan.
Step 1 Take apart the fan by removing the screws on the front panel of your fan and lifting the blades off the hub.
Step 2 Test the switch on your box fan by setting your volt-ohm meter on RX1 and removing the common switch lead from its terminal. Insert one of the probes into the terminal. Remove the other switch leads and insert the second probe into the terminals. Test each terminal one at a time. All readings should be drawing zero ohms. If they aren't, you will have to either replace the terminals, or if you can't replace them, you will have to replace the fan.
Step 3 Service the motor on your fan by lubricating the motor using SAE 20 non-detergent oil. Apply one or two drops to each oil port. Test the motor to see if it is working.
Step 4 Spray the shaft near the motor housing with a lightweight spray lubricant, if your motor is running slowly. Lubrication usually helps.
Step 5 Replace the motor on your fan if your efforts to clean the motor do not work. You can replace the motor by unscrewing the motor parts, taking the old motor to your local electrical store, purchasing a new motor of the exact same model and installing the new motor.
Step 6 Put your box fan back together the same way you took it apart.

How to Fix Box Fan Hunker
http://www.instructables.com/id/How-to-rejuvenate-a-box-fan
Galaxy box fan just stopped Google Search

mcdevito75 here, If the fan is not too old I would figure yes, but a replacement motor will cost as a new fan, if not more, then you have to install and the blades are a presss fit to the motor.

Before you replace it, try oiling it -- look at the little oil hole on the back of the motor housing. Or try taking it apart and cleaning it, then oiling.

Did it work before, but gradually slowed down and then refused to start? See other threads on this topic for that fan model.

The blower motor resistors or fan switch itself are defective.
High speed has no resistors B+ goes straight to blower motor.

If you are up to disassembling your motor, you will find a thermal cutout near the windings which frequently fails open. Replacements are readily available, or just jumper it out. If the bearings are shot or the windings burned you're out of luck. Trust me, a new motor will cost more than a whole new fan.

I just want to know if I can purchase a NEW motor and what the cost is?