those kind of "carbs" are pretty widely used on small ic engines as they are pretty simple to make, i have toyed aroud with building one but never got round to it
i believe there are replacement carburetors readely available on ebay for not that much, briggs 3 bolt carb i think it is?
http://www.ebay.com/itm/398202-Main-Jet-Nozzle-Carb-Briggs-7-9-HP-Emulsion-Tube-2-Pc-Flo-Jet-OEM-New-/151840308366?hash=item235a633c8e:g:BGsAAOSwAodWE935
i've done three competitions without them, for not using them i dont think it looks all that bad. theyve told me that if you have to look back, stop, let go of the steeringwheel and then look back
looks like one of these should fit
# 494622
http://www.ebay.com/itm/Complete-Carburetor-Overhaul-Repair-Kit-For-Briggs-Stratton-494622-/231967856508?hash=item36025c977c:m:mD1O5pZEATeSzWdPGt5NIPQ
take a look through here
https://www.briggsandstratton.com/us/en/~/media/Frequently Asked Questions/Engine/PDFs/Engine Accessories/master_parts_catalog_MS4185.pdf
then when you found it punch the part numbers in the epay searchbar