Booting Debian 10 installer ISO from USB

[prueba@finsakxim.com.mx]

I'm trying to boot Buster installer from a USB by using Grub's loopback 
device.
I already installed grub in the USB and put Buster ISO in its data 
partition.

I read this
https://wiki.debian.org/Installation+Archive+USBStick#Using_GRUB.27s_Loopback_Facility
so I downloaded both hd-media kernel and initrd from here
http://ftp.debian.org/debian/dists/stable/main/installer-amd64/current/images/hd-media/
and put them in same directory as ISO, renaming them as "DebianVmlinuz" 
and "debianGtkInitrd" respectively.

This is my grub.cfg config:

iso_path=/boot/iso/debian-10.1.0-amd64-xfce-CD-1.iso
export iso_path
search --set=root --file "$iso_path"
loopback loop "$iso_path"
menuentry "Graphical install" {
   bootoptions="findiso=$iso_path desktop=xfce vga=788 --- quiet"
   linux /boot/iso/DebianVmlinuz $bootoptions
   initrd /boot/iso/debianGtkInitrd.gz
}

So booting from the USB works; the installer starts. But after selecting 
languages it searches for the installer ISO, but always fails to find 
it. I get "Debian was unable to find an ISO installer image". Even if I 
tell it to browse the specific partition where ISO is it just fails with 
same error.

I also tried loading hd-media initrd in conjunction with Buster ISO's 
vmlinuz kernel, by specifying the loop device instead. Installer starts 
as well but everything else the same: same error.

Can someone help please with this issue?
Thanks beforehand.