I kind of searched for the same parang. With others, I think the Wiseman stainless-and-rubber-handle one is overpriced and probably the wrong materials, to boot. Valiant markets one that is the closest I've seen--it has a water buffalo horn handle, and the blade's both about the shape and size Wiseman recommends in his book. There is a guy (he frequently appears on BladeForums) who has sort of become the U.S. marketer of Valiantco knives, and he has a store on eBay--try a search for "parang" or "golok" on eBay and you'll likely find him. Advantage of going through that guy is that shipping is from the U.S. (if that's where you are), and thus cheaper than from Australia, where Valiantco is or was. The Valiantco parangs tend to cost about $75-85, if I remember correctly; the scabbard is wooden, incidentally, unlike what Wiseman recommends.
I have also read on the forums that very similar knives--same shape, and sometimes well-heat-treated carbon steel--can be had for very little in Malaysia. If you've got a friend who might visit that part of the world, you might have him look around for one.
If the precise configuration isn't essential for you, you might also be able to do much the same stuff with a differently-shaped small-sized heavy bladed jungle knife. These can be had in high quality and low expense in the form of the shorter Filipino bolos marketed at
www.reflectionsofasia.com (you'll have to poke around the site and use the search function to find the bolos, but you can get quite a good knife for about $20 there), or the Nepalese khukuris sold via Himalayan Imports (go to the Manufacturers' forum here on BladeForums, go to the Himalayan Imports Forum, and read through a couple weeks' worth of the posts that have dates on them, usually with "deals of the day" or "blems" or similar indications of bargain offerings. Note the times when these are being posted. Browse some old posts to get a sense of what kind of knife you're looking for--for a 10" bladed knife, the British Army Service (BAS) model is a great, and not too unwieldy, candidate. Then go to the Himalayan Imports site during the times when the proprietress, Yangdu, usually posts the almost-daily bargains, and, if you see one you like, e-mail her with your name, address, which one you want, payment information--and, if you're the first to bite on that one, she'll arrange to send it to you. I'd expect to spend maybe $50-85 on a quite-decent khukuri with lots of character from those guys--hand-forged knives actually made in Nepal are hard to beat for character.
Happy hunting!