For sale, yes. In stock, usually not.
All of the parts can be found here:
GGTS Parts and Accessories
or here:
GGTS Accessories
Looks like CoV is missing the listing for the collector tank right now, so I'll use the links from e-smokeguru. All of the below would be needed to be complete as a GGTS ships, but some of it would be optional depending on what you would want to connect to it. All of these would be required:
A telescope, which would let you extend to use an 18500

A connector (with insides):

A collector tank:

A control ring:

These would be optional:
An extension sleeve (a.k.a. "top tube") to go up to an 18650:

A 510/901 lid, if you plan on using a 510 atomizer:

GGTS Parts and Accessories
or here:
GGTS Accessories
Looks like CoV is missing the listing for the collector tank right now, so I'll use the links from e-smokeguru. All of the below would be needed to be complete as a GGTS ships, but some of it would be optional depending on what you would want to connect to it. All of these would be required:
A telescope, which would let you extend to use an 18500
A connector (with insides):
A collector tank:
A control ring:
These would be optional:
An extension sleeve (a.k.a. "top tube") to go up to an 18650:
A 510/901 lid, if you plan on using a 510 atomizer: