To be fair to the partner here, the water has been muddied by the OP stating that the partner actually sends her his entire wage, so if he needs something out of his own money, he actually does have to ask her for money. On top of that, she states that he is the higher earner and she is actually reliant on his money to help pay the bills. So it isn’t quite as simple as the partner scrounging all her money - it actually sounds like he contributes more than she does, financially speaking, and a lot of the money she’s sending him is actually his money that he gave to her when he got paid.
However OP, that doesn’t change the fact that you individually, he individually, and you both together as a couple, don’t have enough money to fund this trip. It also sounds like in general you are struggling to make ends meet. I think you both need to reevaluate how you deal with your finances going forward, if you plan to stay with him. Culturally, this is likely not the last time he will be expected to send money home/pay for things for family, so it really isn’t a good idea for him to give all of his money to you going forward, as that’s when you’ll end up in another muddied waters situation like this where you are having to use your own money to top up his. He should have his own separate savings account to deal with his family things, completely separate of you and your money. You both need to look at your financial responsibilities as a couple e.g. rent, bills etc. and work out if you can afford these without him needing to send you everything, so he can keep a bit back for his family savings. That goes for you too - you both should be entitled to have your own personal savings pot, outside of each other, especially when you’re not married. If you’re not able to do this, you both need to look at further financial support that may be available to you, he could look at trying to find a better paying job, you could look at any benefits or help you might be entitled to due to your health issues, anything at all that would put you both in better financial standing. The current situation isn’t working, and while it’s obviously incredibly stressful, the only way you’re going to be able to get out of it is to tackle it head on.