For wall hanging or a costume, length and weight are not an issue. For light tree-branch trimming almost any HI blade will do fine, especially 15 inch or longer, but you don't need anything too heavy. You'll get more stress relief if the blade doesn't tire out your arm too quickly.
With these comments in mind I recommend an HI Chitlangi in the 15-16 inch range. That's overall length, not blade length. The double-fuller Chitlangi is one of the most beautiful blades made by HI, hence excellent as a wall-hanger and costume accessory. It is also well-suited to light tree-branch trimming. Yangdu posts Chitlangis for sale at this forum quite often, in a variety of lengths and weights and at reasonable prices. Some come with polished blades, and some with satin finish blades (called "villager" models). Here are some of mine:
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The first blade is one of my all time favorites. It checks all the boxes: looks, length, weight, versatility. The first and second blades pictured are each about 16 inches overall length and weigh 16 oz. The main difference is the blade finish: satin with steel fittings, and polished with brass fittings.
The third picture shows a larger Chitlangi: 18 inches overall length and 24.5 oz. Also great for light tree-branch trimming.
The fourth picture shows another favorite of mine. It's called a Chitlangi Tanto, but it's not really a Chitlangi except for the fuller, nor is it a khukuri. Tanto, yes. It is a short-sword made by Lokendra, one of my favorite HI kamis (unfortunately, no longer with HI). Overall length is 21 inches, weight is 35 oz, steel hand-guard and buttcap. A powerful blade, possibly one-of-a-kind, probably made for someone as a custom order. I got it second hand, so I don't know its history. The handle is chiruwa-type (full tang) with wood slabs (probably satisal) and a tennis racket wrap that makes it nice and grippy. I don't remember what I paid for it but the sheath alone (made of very thick leather) was worth the price. It doesn't really belong in this thread, but I like to show it off.