I don't know if this will help but...

New England Wildflower society teaches a course each year. May be the instructor of the class could help you. He may sell them on the side. You could call NEWFS.

Here is the description of the course:
RUSTIC OBELISK AND TRELLIS SDW3003
DESIGN WORKSHOP
Garden in the Woods, Framingham, MA
Sunday, June 25, 1Â5 p.m.
Learn how to build your own rustic garden
structureÂyour choice of an obelisk or trellis. Beautiful and
natural, it will complement any garden. Furniture maker
Frank Hamm will show you how to collect wood, and then
guide you through the process of design and construction of
an attractive, sturdy structure. Techniques covered in this
workshop can be applied to building other rustic furniture.
Enjoy the outdoors while learning a skill that you can use to
enhance any garden or home. Bring gloves, measuring tape,
hammer, pruning saw, and a portable electric hand drill (if
you own one). Extra tools will be available. Parent/child
pairs are welcome. Cosponsored with the Cambridge Center
for Adult Education.
fInstructor: Frank Hamm, furniture maker
fFee: $75M/$85NM includes all materials for one project
fLimit: 20 participants

Thank you so much Sedum, I will try to check that out. Have you taken the course yourself?

No I haven't taken this particular class but have thought about it! I've taken other courses at NEWFS and have been happy with the quality of the instuction.

Sue

I'll be back in a bit with info...I know someone who does these...