Proposing - What are feelings on a placeholder ring? Good morning!

I am looking to propose to my partner (F 30) for 4.5 years when we go travelling next month. I have given it a lot of thought, but one thing I am still unsure of is the ring. Given where we are travelling (inc trekking the jungle) I just don't feel comfortable bringing an expensive diamond ring with me, and I would also like her to be involved in choosing the ring for herself.

So my questions are:

**A)** Do women generally look down on a placeholder ring?

**B)** I am stuck on going down the Cubic Zirconia route so it looks closer to what she will get later, or instead make it very clear it is a placeholder ring (i.e a gemstone ring). What would women want to receive?

I'm a bit lost and a women's perspective would be appreciated. 

TL;DR What route should I go with a placeholder ring?