Hey a topic on here I actually have some expertise in !! It has been a while since I have posted on this forum.
You can buy left handed safeties from several sources.
midwayusa has them for about $15.00
Also Numrich
http://www.e-gunparts.com/DisplayAd.asp?chrProductSKU=931440A&chrSuperSKU=931440&MC=If your gun is an older one it may already have the hole in it that allows you to switch the safety.
If you are lucky enough to have both holes then switching is easy.
If not you will have to buy the left hand safety or drill two holes. I do not think that there is any reason to plug the old holes when doing this. I know that some people do as Bill suggest and plug the old holes, but then you can't switch it back.
The Wingmaster that my dad bought new in 1972 has the second hole.
My 1980's 28ga Wingmaster does not.
See the pictures.
p.s. Didn't you try to buy a left handed safety a year or two ago from some yahoo that I recommended? I feel bad about that again... At any rate I have used the one from Numrich and it works fine. and I am sure they will not rip you off...
sigh...