I have to begin by saying if you are having trouble driving a pin out, it nearly aways means you are not supporting the housing rigidly enough, or you are not using the right punch.

If you are going to be doing the job regularly, the right way to do it is to get the right tools. Begin by determining the actual diameter of the pin you are trying to punch. If this is a made-in-USA Tecumseh, it will be inch size. Later Tecumsehs were mostly rebranded Italian engines, and will be metric size. In general a punch marginally smaller than the pin has advantages: it supports the pin as it is being driven out, and you can use it as an aid to reassembly as well as disassembly: you let the roll pin push the pin punch out of the hole, as you drive the pin in.

Now, in selecting the product, brand and supplier, the first point to remember is that you need parallel punches, not tapered ones. Tapered ones have few uses, and certainly don't suit your current purpose. The second point is, buy decent tools that will last as well as possible, and have as flexible an application as possible. That means choose chrome vanadium alloy. It also means make sure the round, parallel section of the punch is a sensible length: at least as long as the pins you plan to drive.

Here is an example of a set of punches that is well-priced but may not extend to a large enough size to suit your needs:
http://www.ebay.com.au/itm//201074112084?pi=466130

Here is a second-hand set that may be pretty much what you want:
http://www.ebay.com.au/itm/Mechanic...?pt=AU_HandTools&hash=item2341428b0b

Here is a set that seems to be properly made but seems to be plain carbon steel rather than Cr-V steel, which implies a shorter life and much less tolerance of abuse:
http://www.ebay.com.au/itm/6PC-HEAV...pt=AU_Hand_Tools&hash=item53ed5c3960

I'm not recommending any of these products, I'm just explaining how I go about sourcing such things. You will notice that I've focused on items that are already in Australia, because if you import an item, it has a standard delay of 2 weeks in Australian Customs, so it takes 3 weeks to reach you.