The relevant rules are here: https://2e.aonprd.com/Rules.aspx?ID=587
It looks like you’re looking for this text:
If you choose, you can allow the player to instead start with a lump sum of currency and buy whatever common items they want, with a maximum item level of 1 lower than the character’s level. This has a lower total value than the normal allotment of permanent items and currency, since the player can select a higher ratio of high-level items.
So, Rules As Written, your choice would be to either take 25gp and a second-level item and two first-level items, or a lump sum of 75gp with which to buy items.
(Comparing levels 1 and 2 on that table, it looks like the rules believe that a first-level item is worth 10gp.)
Your other option would be to take the most valuable first-level item (the 18gp Half Plate) and sell it for half price.
There don’t appear to be any rules for exchanging permanent item draws for anything else. This is the sort of thing that you could ask your DM about, but my prediction is that your DM will tell you that they’d prefer that you take the 10gp or 9gp, rather than issuing homebrew for it.