Hi mate, there is so much choice. first there is size,its my opinion that with the size of a bus you need 6 inches for them to look in proportion.like alot of things mate it depends on ££ and your out look - you can get cheap sets or branded sets, repo or genuine vintage,NOS boxed brands like Wipac,Hella,Lucas,Bosch etc spot lamps go into the hundreds, which is a big gamble considering they are in direct aim of flying stones etc. stainless steel bodied lamps will last longer obviously.
Spot/driving lamps normally go up with the headlighhts and come on with the main beam. front fog lights are normally positioned low down so they project light 'under' the fog. some foggy's are yellow as it is belived to cause less reflection from the water droplets but many argue that it makes no difference and it was a trend.
my plan is to have a pair of 6 inch round genuine 60's 'LUCAS' FT/LR 10/11 spots mounted to a badge bar above the bumper and a pair of small sqaure lense 'WIPAC' yellow fogs at the outside under the bumper.the spots will be through the main beam but the fogs wired indipendantly6 with a proving lamp on the dash.
hope this helps.
just some random examples on Eaby at the mo.............
http://cgi.ebay.co.uk/HIGH-QUALITY-CHROME-CLASSIC-HELLA-SPOT-FOG-LAMPS-70s_W0QQitemZ130269739523QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item130269739523&_trksid=p3286.c0.m14&_trkparms=72%3A1301%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318" onclick="window.open(this.href);return false;
http://cgi.ebay.co.uk/LUCAS-SQUARE-8-SPOT-LAMPS_W0QQitemZ110314859415QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item110314859415&_trksid=p3286.c0.m14&_trkparms=72%3A1301%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318" onclick="window.open(this.href);return false;
http://cgi.ebay.co.uk/CLASSIC-MINI-DRIVING-LAMPS-FOG-SPOT-LAMPS-PAIR-S6007_W0QQitemZ270090624663QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item270090624663&_trksid=p3286.c0.m14&_trkparms=72%3A1301%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318" onclick="window.open(this.href);return false;
http://cgi.ebay.co.uk/Spot-lamps-Halogin-quality-metal-backed-7-raydot_W0QQitemZ260307841517QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item260307841517&_trksid=p3286.c0.m14&_trkparms=72%3A1301%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318" onclick="window.open(this.href);return false;