Considering what is involved in building a machine, the fact that you haven't as yet ordered any parts & may not even have a suitable design sorted then you are asking a lot if you need to be up & running in 3 to 4 weeks, it would also depend on how much time you could devote to the build & what sort of tooling you already have to actually build it.
As for what is available commercially sorry can't really help but a lot will depend on the type of work you want to be doing & the materials you need to be able to cut.