Unfortunately, CL only has a limited set of stream types built in. The file stream and string stream are the basic types. The broadcast-, concatenated-, echo-, synonym-, and two-way-stream types allow for chaining and composition.
If you want to use the stream API, and your pattern doesn't fit in the standard classes, then you probably want to use Gray streams
Flexi-streams adds a layer on top of Gray streams that you probably don't need based on your current description.