Ruger Single Six Hunter

Brucear,
I'm not sure if the front sight is fixed or replaceable on the six, but if it's replaceable, it's pretty simple to go with higher and wider blades.
There are a number of sights available, depending on your preference. X-S sights makes a very good express sight system for wheelguns, Marble arms offers a wide variety of heights and styles, and there are others. You will find a good selection in the Brownells catalog, or contact the manufacturer directly. A very good source for specific Ruger revolver parts in general, and one that helped Mike here is Power Custom.
Any decent search engine will take you to their web sites.
A lesser solution, one that doesn't work for all light conditions, but doesn't require anything beyond a steady hand, is to paint the visual surface of the blade. There are some brilliant colours available, just have to go slow because the paint does run.
Hope this helps.

brucear: Ruger sells a set as listed in this link. You might also be able to find just a front sight other places as Mak suggested. Chris S
http://shopruger.com/Single-Six/products/3220/

as in the fine print at the bottom of the listing, darnitall.  I'm also looking for a sight for my SS Hunter. 

I have used the florescent paint on a couple of different sights, clean well, clamp the gun with as much of the blade level as possible and apply several thin coats allowing to dry, good results... 

Thank you!
Simple solutions sometimes are best - just not thought of. 

I've used paint for years, and so have others. Like I said above, there are some new light catching formulas, but they vary in effect and durability. It's hard to beat good old Testers hobby paint for all around effect. It's durable, picks up light well, and looks good. For thin and Patridge styles, let it thicken up in open air, and apply with a toothpick. Couple coats is all it takes. It'll look as good as your hands are steady.  
Good luck 'n' good shootin'

Brucear,
I was just recently having the same problem with my 61 year old eyes, and a couple blue steel 357's.  Don't remember where I read this, but a fellow said he had great success with flouresent/bright finger nail polish.   And my wife just happened to have an old bottle of Orange Dreamsicle..perfect.  And comes with its on applicator.   Though I did just order the white and orange sight markers, with a set of skinner winged sights, for one of my Marlin lever actions.  The directions said try one/base coat of white, then two coats of the orange, for best results.  Good luck sir.
Bill