These 2 extenders are all I have so far. For these 2 I am using the Breadboard Prototype PCBs available at Radio Shack (276-0150). The one with the switches on it also has several female pins soldered to the board so that the switches can be configured with a pull up or pull down resistor. These resistors can be changed as needed. The switches I got from Electronic Goldmine a few years back, they were 5.00 for a bag of a 100. I have them mounted on their backs as opposed to their feet which faces the bus lines.

The extender with the LEDs on it has one set of LEDs (8 red ones) that are hooked with the same female pins put are used individually with a resistor mounted on the board via the female pins. I use the female pins to put the resistor in so it can be changed if need be. The other set of LEDs are the clear ones, but light up green. There are 11 of those on their side of the board and they use the 2 center bus lines to connect to. Again I have the female pins soldered to the board so that the leds can be used from the gnd bus or the VCC bus with a dropping resistor and another point to actually control the LED.

The female pins are from amazon: http://www.amazon.com/40Pin-Single-2-54mm-Female-Header/dp/B00ZBS4T12/ref=sr_1_2?ie=UTF8&qid=1453610774&sr=8-2&keywords=female+solder+pins+headers

Well it seems Amazon has gone crazy about the way they are pricing these female headers. I got 10 for 7.91 back in 2014. The prices on amazon seem to be out of control as of now (1/24/2016).