Lens Shaped Chisels

[frogwalking]

Looking at Tallbear's inletting tutorial, as well as Acer's carving tutorial, both use lens shaped chisels.  Can I buy these, or must I make them?  If it is the latter, from what kind of chisel, do I begin the modification process? 
This method appears to be a less expensive alternative to buying $4oo worth of different sized curved gouges.  Is this a correct observation?  Thanks all for the responses.

Frog

[Acer Saccharum]

I think you must make them. 

[Larry Luck]

Here is a link to Gary Brumfield's website  http://www.flintriflesmith.com/ToolsandTechniques/shopmadechisels.htm (thank you Katie for keeping it going).  There are several photos of the chisel aka "Gary's little stamping tool" that will help you making one for yourself.

Larry Luck

[PPatch]

I made mine out of old, small, screwdrivers. They won't replace many gouges but they are a good tool to have on hand, I use them for wire work.

For inlays I use an exacto knife to cut in around the shape, then a 1mm/16 gouge to relieve immediately inside the cut. For the rest I  employ a sharp 1/4in parting chisel and this:

https://www.toolsforworkingwood.com/store/dept/TXQSS/item/IL-RAYGHS.XX

The palm version.

dp