I wouldnt (couldnt) fly without a suitable kneeboard - sort of like a security blanket! The only one I have found satisfactory for helicopters is made by Sky High Gear. What makes it work so well, among other features, is its small size - will even work in a toy helicopter (R22)
Made of ballistic nylon with sewn in padding on backside to conform to leg. About 5in x 7in size with several loops to hold pens and a small flashlight, etc. Velcro is used to allow a certain amount of customization (right knee, left knee, right handed, left handed) etc. I checked
www.skyhighgear.com and dont see this listed. Possibly discontinued, but I see it is still available at my local pilot shop. Best of all, about $30 U.S. If you need a "kitchen sink" kneeboard (will hold every possible piece of flying gear) this may not be for you, but otherwise highly recommended after trying almost every kneeboard known to man.
ADDITIONAL COMMENTS: This kneeboard is part of a "system" I have evolved over decades of plank flying, and more recently have adapted to helicopters. One of my SOP's is to have on board a written (printed) trip plan for any flight that leaves the traffic pattern of my home airport. This includes charts (enroute, approach, airport diagrams), detailed flight log, W&B, comprehensive printed wx brief, etc. This may seem like a great burden (and perhaps overkill) for shorter flights, but it is a 3-5 minute execrise with modern flight planning software. I use Jeppesen FliteStar and it readlily prints all of this in kneeboard size as a "trip kit." As far as it being overkill, maybe, but reviewing this material before flight is something I consider a "safety enhancement," and if something unanticipated happens during the flight, much of what I might need in the way of info is right there on the kneeboard. While I carry "official" paper charts on board for every flight, with an FMS, back up GPS and the Jepp trip kit, I very rarely have a need to open a chart in flight (usually to locate an obscure intersection in an amended ATC IFR clearance). I find that rule-of-thumb calculations done done in the head are more than sufficient in flight, and cant imagine trying to use a whiz wheel or even a calculator flying a helicopter single pilot (unless, perhaps, equipped with an autopilot). No doubt, more than most wanted to know!
