It's a dilemma, because they are affordable, and more useful for small trades, eg buying some food in teotwawki, but they cost twice as much per gram as buying a gold sovereign, which is about 4g.
The other thing to watch is the purity. They usually tell you how much actual weight of pure gold it is, eg 7.98g sovereign, containing 7.322 g pure gold.
Cheapest there is 1g Chinese Panda, 2024, £99.50, 24 ct, 999.0 fineness. This is considered pure gold. It is 99.9% pure. It is marked Au 999. Au is the chemical symbol for gold.
There is also an Armenian Noah's Arc 1g coin on that website that's even purer, at 999.9 fine, but is still considered 24 ct.
NB. There are also 1/20th oz Chinese Pandas, which are 1.55 g 999 fine.