I made a similar drier years ago based on an article in an EAA magazine. Just an aquarium pump from the pet store, a 1.5L soda bottle, Tygon tubing, fittings and indicating Silica. I use round plastic pill bottles to cap the exhaust pipes. Dry the desiccant in an oven at 240F when it turns pink (some guys on the field use a microwave, or a crock pot on high). Been doing this on 3 different planes over the past 15 years.
RV4 - Bought 2013 Sold 2017 after 450 hrs
RV7 - Built in 6.5 yrs & Flying 2017