Where can I get a FA3-4 Ryobi grinder on/off switch or an equivalent

bunnings have exclusive rights to ryobi
take the details to their special orders counter and have them order one in If it is available
if not available you may get one from e-bay overseas
a switch is a switch and the voltage is not a problem as you have a part number ,
you may get one from tool parts shop so go google and type in ryobi spares and there are sites in Brisbane that have parts for a range of tools including ryobi, if not in other states

go google and type in--- parts for ryobi 4 " angle grinder model eag 95
I recently spent may hours searching for parts for ryobi angle grinder 4" that is close to 45 years old and saw plenty of sites for ryobi and others that carried listings for many ryobi grinders
I suspect that you will be lucky as you have a model where as I didn't have that luxury

Handheld grinder or bench grinder? I'll assume you're asking about a handheld grinder.

Engage the arbor lock. You may need to rotate the wheel until you find the spot where the arbor lock locks the wheel. Use a wrench or a gloved hand to unscrew the wheel (I use my bare hand). Screw the replacement wheel on and disengage the arbor lock. The new wheel doesn't need to be very tight, it'll tighten itself as you work.

The switches I have seen can not be repaired but replaced.

The switch is probably generic.. go to a Lighting store and see if they have equivalent

You can purchase replacement carbon brushes on amazon Amazon com Ryobi carbon brushes. I hope this was helpful. cheers

Google ryobi stores. I'm in az and they have them here. Or ryobi repair and your location. I went to the dewalt replacement shop got a trigger for my angle grinder for under 2 dollars.

The Grinders are made by TTI they will be able to get you replacement brushes. But to be perfectly honest its not worth repairing a 4" Ryobi they have a rather short lifespan and are not balanced very well. The cost of brushes and shipping may be very close to that of a new grinder, espicially if you need a new armature.

TTI can be found here:

http://www.ttigroup.com/en/our_brands/by_division/power_tools_and_accessories

Cheers,

http://www.allproducts.com/prc/taihu/fa3-4.html

You should be ablt to find it at anylowes or home depot.If for some reason thet do not have one I would call the local industrial distributor like grainger or msc