### This contains spoilers!!! ###
This is a very good point. Something I quickly realised while playing the game. The cheat for talismans only works if you have a talisman in your inventory at the time.
There are more talismans hidden around. Chapter 1, when you go into the underground water pathway, there's a panel on the second foot platform that you can blow up which has around 7 talismans in it. There's also about 5 you can get from the old women in the factory if you find her diary.
Something else I want to mention.. During battle, if you're lucky enough, you can beat all the bosses with just 1 round. Use Running Scale and then Shining Fang and then finish with Claw Strike. If you're lucky, the first 2 attacks will bring it down to 1/4 health, and claw strike will finish it off. You could also try doing Claw Strike first and then Running Scale and Shining Fang.
Don't forget there is a second path to take in the game... When you get to the Twins at the end of the waterway, choosing to fight or not will determine who you travel with and where you go.. so there's still another location you haven't been to yet 
Awesome post, thanks. The first time I played, I picked yes to fight the girls. At the end, I was short maybe 4 or 5 talisman but had enough explosives. In fact I had one left over with enough material to make one more, actually!
Today I played again and picked "no" to fight the girls. This time I had a surplus of talisman, I had 10! Even crazier, was that Before fighting the guardian in Egypt I had around 18 or 20 still! But I was short by 1 explosive with not enough material. In the room with the two mummies before getting to the sun and moon rooms, I had one explosive only, ugh!
So overall, I would say the game is poorly balanced and not much room for error. I had to use Ritchies cheat 7E928209 just for one exploding can. I did not need unlimited, just one more! I really hate that, but what can I do? ughh! Maybe I missed a place for one more exploding can (I got the 5 from that one guy after beating the first boss but there does not seem to be another place to get them in the waterway or chapter 2 or 3. Chapter 2, you need a lot more exploding cans for the "no" path than the "yes" path, which is part of the issue. Again, slightly poor balance.