I bought the lamps through this place as they had the best pricing.
http://www.classicgarage.com/accessories.html
One of the challenges was finding lamps which were not too small or too large. The Hella Optilux 1300 model I used are just under 4" diameter.
Another challenge was finding material to use as the "cans". A visit to my buddies at P&P Performance in Tomball resulted in a scrap piece of 4" tubing which worked great. The tubing is 4" OD. The ID provides about 5/16" of clearance around the lamps. Getting the tubing to fit the backside profile of the bumper was tedious as was getting them square and pointed straight. I designed adjustment in to the installation so I can fine tune the aim in all directions.
There were other lamp options but I am not a fan of blue tinted lights or the halo style. Rather keep things subtle. The Hella lamps came in a kit with the wiring, relay and switch.
I had a chance to use the lamps Friday night on a trip up to Decatur, Tx for a swap meet and social. They did help but still need to adjust the aim to maximize the benefit. At this time I do not have a shot showing how well they throw light.