I have never run wire to patio speakers outside. I have always fished it from the inside out, directly to the speaker. However, in this case I have to. The run is about 35 feet, coming up from under the deck, up the drainpipe, across the top of the deck to the speaker. I am going to use low voltage landscaping wire which is black. It blends in well with the deck, so you will hardly see it, but what can I use to tack it up? I cannot find anything that will fit around the wire exactly. It's an odd diameter. I want something that will blend in with the wire and keep it nice and tight. Any ideas? Thanks.

Whats the surface? Brick, wood, sideing?
You say you are going across the deck to the speakers. Are the speakers sitting on the deck?
Also, why not use direct burial with a black jacket? I bet Fred has some laying around.

When I have an odd sized wire I'll use my T-25 stable gun to stable tie wraps along the path I want to run the wire at about 1' intervals then wrap up the wires.

Use conduit and solder the connections @ the speaker.

This topic came up not to long ago, Larry suggested the low volt lighting cable, but cautioned that it is most likely not CL 2-3 rated, I would also agree with that.

Use direct burial cable, class rated and will withstand the elements.

my .02

Use conduit or PVC pipe. If this is a outdoor deck application then I'm sure they will be hosing it down all the time which means in 6 months you'll be performing a service call.

I am using direct burial. It is black. The speakers are 10 feet off the ground facing down (or will be). The wire is an odd size. I will be attaching it to wood, but there is only about 3/4 of an inch, so whatever I use, it will have to fit in that area. I would like to use something black, but I cannot find anything. Someone suggested outdoor staples painted black, but I don't really want to do that. Conduit is not really an option as it will stand out too much. Media1, I might give your suggestion a try. I often do that when I have many wires together on long runs in the basement, and just zip tie then to electrical staples. It works pretty well. Well, if anyone has any more ideas, let me know. Thanks.

I think stapling the tie wraps is a really good idea in certain situations.

Or using the zip-ties with the screw holes already in them and putting a screw through them?

You could also use the tie wrap pads that screw down and has a slot for the tie.
Just keep in mind over time tie wraps especially outdoors will get brittle and break.
Personally I would go with conduit and clamps.