I need a folding knife that I can open one-handed with a blade of 4.5 inches or longer. I tried the Pocket Bushman but I can't open it one handed. I've been checking the knives offered in the net and I can't find any knife that fits the bill. I will appreciate any suggestion.

How about the Kershaw Blur in S30V. It is smaller than the specified 4.5 inches in blade length but the S30V will more than compensate for a slightly larger blade in 440C for example.

http://www.knifeworks.com/kershawbluraluminumhandlewtrac-tecinserts30vstonewashedplainedge.aspx

That is a GREAT knife. I recently lost mine after 4 years, and I'm replacing it.

Be more specific. Left or right handed? Clip or no clip? You want assisted opening or not? Thumb stud, hole in the blade, etc? Any preferred steel? Price range?

Spyderco military version is about the right size. Cold steel Voyager is also about that size. Both right handed, non-assist opening.

Best bet is to go to a local knife store, if you have them. Play with lots of knives. Then order for $15 cheaper online

sounds like you have a cold steel dealer in Argentina where you live, try the New Generation of the Voyager, they are now ambi-clip after years of no change. One hand opening in various blade length at a reasonable price.

Right handed. Clip irrelevant. Ditto assisted opening. Thumb stud preferred but hole in blade acceptable. Any steel. Up to $150. Minimum Blade length 4.5" MANDATORY. Plastic handles unacceptable. Weight irrelevant.

I'm in Argentina. Lots of fixed blade knives available, but good folders are scarcer than hen's teeth.

I'm going to buy the knife on line from a U.S. source.

For cheap but solid, the Byrd line by Spyderco. You're going to hard pressed to find folders that big - I think the biggest they have is a 4". As for the other requirements, I think you may have to have a little flexibility.

http://www.knifecenter.com/kc_new/store_detail.html?s=CS62KG
http://www.knifecenter.com/kc_new/store_detail.html?s=CS21S
http://www.knifecenter.com/kc_new/store_detail.html?s=CS29XXC
http://www.knifecenter.com/kc_new/store_detail.html?s=BM741BK
http://www.knifecenter.com/kc_new/store_detail.html?s=BM760BK
http://www.knifecenter.com/kc_new/store_detail.html?s=BM13220

Mainly, just look through every page...

You may Like to try smkw.com,They have been around for a Long Time! Good luck! I have no Affiliation with the above!

Not that it's critical, but since DR has moved his knives from aeromedix to knifeworks, I've started looking there more often. So far I like what I've seen.

Knifecenter/Victorinox Swiss Army Sentinel

This fits most requirements,blade is 4 3/8",locks,one hand,$20.

Looks good to me. Simple, solid, functional. The sort of thing I might select for myself.

The Maxpedition Rollypoly caught my eye.
http://www.knifecenter.com/kc_new/store_detail.html?s=MX0233B