The current cap is just a standard PVC cap that I can find at Home Depot for 50 cents. However, none of them have 1/4" threaded holes. I am not mechanically inclined, so I do not know if I can ...

It comes in 3-, 4- and 5-inch sizes and costs about $10. One of these sizes should fit your vent. The caps are round with protection around the top and sides to prevent water penetration.

Go back inside and connect the dryer duct to the vent cap pipe (a 90-degree elbow may be needed), securing the connection ...