Yes it can be done with two normally closed relay( 1 for each side)
Normally there are three type of wire's to back lights bulb.
1- side indicator light
2- reverse light
2 parking light
May be this way :
Connect switched wire of parking light to side indicator wire. Do on both side.
This will turn on indicator light when parking light is on.
Install relay in between indicator light and operate this relay from original indicator wire.
This will blink indicator light when required.