Be careful!
Because I drive a BMW Z, I have found a lot of "Z" Stuff. Let me know about links and products for other roadsters please.
As one travels this great land, we begin to understand more about "stuff". We start out life without any stuff of our own and as the years go by we seem to accumulate more and more stuff. We always want to take an amount of our stuff when we travel. Stuff like shirts, underwear, pants, toothbrushes etc. seem to be important to us and we need this stuff when we are traveling. It seems that roadsters of all makes and models simply have less space in them to put stuff than most other forms of transportation except perhaps the motorcycle and bicycle.
There are a few solutions
1) Trunk Racks
<Click
on Photo> Here's a Z4 with the BMW "official" Trunk Lid railing
System. The BMW Rack is shown attached to the rails. The rails need
to painted to match your Z and then the trunk drilled to fit the
rails. This solution is available at your BMW dealer.
<Click
on Photo> Here is the Rack with the BMW Suitcase installed. You can
click on the photo(s) for a better view. This solution is available
at your BMW dealer.
(NO
DRILLING) <Click on Photo> Here's a Z4 with a clamp on rack. The
rack clamps on to the left and right sides of the trunk lid. I found
this at
Roadster Solutions <Click Here>. I found versions of this at
www.sportsimportsltd.com <Click Here> and they have add ons such
as bike racks etc for sports cars.
2) Trunk Racks (Z3)
<Click
on Photo> This is the removable clamp on rack for the Z3 (I do not
know if it will fit a a Z3 M Roadster. I found this one at
Roadster Solutions <Click Here> I wonder if these will fit
the Z3 M ?
<Click
on Photo> Here's the Z3 "Factory Rack". Drilling is required. I
assume that when one takes the rack off that there are hole plugs to
cover the drilled holes? Does anyone know?
<Click
on Photo> Here's the factory rack above with the hard suitcase
installed. This is also available at
3) Trailers (Z3 Only So Far) I have not found a Z4 trailer hitch.
<Click
on Photo> Z3 Trailer Hitch. Available at
HMS Motorsport <Click Here>. Also found (less expensive) at
www.hitchsource.com <Click Here> as well as an installation
instruction. <Click
Here for Instruction Sheet>
See photos below from Bob Koch (taken at Homecoming). I assume the
trailers are from motorcycle dealers? 
CLICK ON PHOTOS.
4) Deluxe Roadster Valet & Between Seat Bags
<Click
on Photo> The Deluxe Roadster Valet can be found at Roadster
Solutions. See
The Deluxe Roadster Valet <Click Here>. Holds approximately 8
garments with space for shoes and accessories across bottom. Two
shoe bag are included.
Z3 and Z4 Between Seat Packs
<Click
on Photo> The Z3 and Z4 Between the Seat Packs are available at
Roadster Solutions:
Z3 = <Click
Here>
Z4 = <Click
Here>
