There are numerous options for electronics with your pack. It isn’t necessary for your pack to have sound or lights, though undoubtedly the effect is very much welcome.
In terms of lights, there a few sellers who offer superb light kits. www.gbfans.com offer their own electronics kits with the beauty of these being that they simply clip together, requiring no soldering at all. They offer lighting and sound kits, both of which interact with each other and offer a number of modes for you to tweak and tailor your pack to your liking. These include all the video game sounds and modes, colour changing barrel lights ( in order to get colour changing pack lights, you will need to buy the expansion kit from the creator of kit, Spongeface. You’ll find him on the for sale section on gbfans) and an interactive mode is also and additional feature on the board. A random ghost sound will play and if you’re quick enough to fire, you’ll get a quote from the movies, how cool is that?
Prop Forge offer what some consider to be the most screen accurate lights available. Some soldering knowledge is required but for the most part, the kit is plug and play. You’ll find his for sale thread on www.gbfans.com. Jupiter electronics operates out of ebay and offers some fantastic and very affordable light kits.
Most of these kits can be installed with very little soldering. Crix, who also operates out of www.gbfans.com also offers both sound and light kits. These require a little bit of electrical knowledge, but nothing overly taxing. His for sale thread shows how to wire his kits up correctly.
The mightymicro kit can also be used to make pack lights and sounds. This kit is highly customizable, allowing the user to add their own custom sounds to the chip. So if you have a particular firing sound you prefer or a switch on sound you like, you can add this to your pack and tweak to how you like. The kit does require a little bit of adruino knowledge, guides of which can be found on gbfans.
These are recommended kits, but is by no means an exhaustive list. There are other sellers who offer kits too and if you are skilled enough to build your own electronics, fantastic!