I ordered a 870 Express Synthetic 7-Round in a 20 gauge configuration. Is it possible to mount a scope? If so, where do I look for the mounts?

The simplest option is to order a B-square or similar mount from www.cheaperthandirt.com www.midwayusa.com or www.brownells.com .These mounts simply replace the trigger group pins and take about 3 minutes to install BUT aren't meant for extreme precision,which from your post don't sound like you need.