Hi there,
With regard to load balancing are you talking about IP, application or route load balancing?
If it is the latter any, cheap ISR (1841, 880 series) will be capable of protocol-independent and protocol based route load-balancing.
You may be better off just using an emulator like GNS3, EVE-NG or VIRL instead of purchasing hardware.
cheers,
Seb.